Hello guys my macbook pro 2015 13 inch have a weird problem

If the liquid sensor has been tripped and is showing a bit of pink or red, then most likely liquid has made it into the laptop. Most likely if you look closely that you may see small bits of corrosion forming on some of the solder joints for the components. Sometimes it can be extremely hard to see even when using a magnifier as it can be as small as a speck of dust. Even if no corrosion is visible, it can hide under some of the chips since some chips actually have solder joints underneath them hidden completely from view.

I was actually thinking of possible liquid damage when replying before, but did not mention it since so many people get upset when I suggest it as a possibility...so I tend to avoid mentioning it. I have learned when you see certain behaviors it has a higher chance of being caused by liquid damage. For the issues which are really odd & don't make sense, those have an even higher probability of having liquid damage being involved. I see a lot of accidental liquid damage while supporting thousands of our organization' computers. All it takes is just one well placed drop of liquid splattering into a vent of the laptop.

I think you have definitely pinpointed the source of the problem. It is still a very odd failure with how it behaves, but I'm guessing it is due to how the video is handled pre-boot versus later in the OS loading process. In the pre-boot time, the laptop's firmware is using a very basic video output & buffering compared to when macOS loads a full fledged video/GPU driver.

If there is no video on the built-in Display, then make sure the brightness is not set too low. Even try a PRAM Reset (hold the PRAM Reset for at least three chimes) to see if it resets the backlight brightness. If the backlight is bad, then you may still be able to see very faint images on the display if you look really closely...best to turn down the room's lighting which can make it easier & minimize glare. You can also try shining a bright light onto the white Apple logo on the back of the display to see if it can provide enough backlight for you to navigate (sometimes shining the light on the front at an angle and viewing at an angle can allow you to see faint images. Best time to look is during boot when you have the Apple logo displayed at the center of the screen. The login screen and desktop can be very hard to see clearly enough.

If the built-in Display is bad, then try connecting an external display. Unfortunately Apple does make it extremely difficult to get full video to the external display, but it should be possible one way or another. You will most likely need to enable mirroring to properly use this laptop with the external display. You can try using Command + F1 to toggle display mirroring on & off, but sometimes this is not an option until after logging into a macOS user account (especially if Filevault is enabled). If you get partial video on the external display, but System Preferences launches onto the broken internal display, then you can right-click or control-click on the System Preferences icon on the Dock and selecting "Displays". This will display a Display setting window on the external display....just click "Gather Windows" in order to bring the main System Preferences window to the external display where you can select "Mirror".

Unfortunately if the password reset screen appears since you failed to log into macOS previously, then you will not be able to do anything with the external display until you can reboot the laptop by clicking "restart" button on that window (a PRAM Reset may also remove the password reset screen on the next boot). Even if you can log into macOS, a system setup screen such as those after some OS updates can prevent any access to macOS until those screens are passed through.

You can try to use Clamshell Mode to force all video to the external display. Clamshell Mode requires connecting the charger, wired USB keyboard & mouse, and external display. Then closing the lid of the laptop to force video to the external display. Theoretically this can be done at any time in the boot process & even while sitting at the log in screen or even desktop, but I have found sometimes it may be necessary to trigger Clamshell Mode during the early boot process by closing the lid of the laptop immediately (within a few seconds) after hearing the startup chime.

If your login screen shows icons for various macOS user accounts, then you can type the first character of a user account name and pressing the "Return" key which will select a macOS user account beginning with that character. You can now enter the password for that user account and press the "Return" key to submit the password. This works assuming you don't have more than one macOS user account beginning with that character (I don't know how macOS determines which account it would select if multiple accounts begin with that same character). You can also use the arrow keys to navigate to the desired user account if you can recall which position the user account is at.

Thanks for the video. That is very odd.

Definitely try using an external display and using Clamshell Mode as I described previously to see if the same thing happens when using the external display since this is about the only way to see the early boot screens especially when Option Booting. I sometimes even have issues with Clamshell Mode when trying to see the early boot screens.....sometimes I have to disconnect the internal display cable so all video automatically goes to the external screen. The internal video cable connector on the cable & connector on Logic Board are very easily damaged which is made worse by the award position when reconnecting them, so I don't recommend most people disconnecting it.

You can try to use Clamshell Mode to force all video to the external display. Clamshell Mode requires connecting the charger, wired USB keyboard & mouse, and external display. Then closing the lid of the laptop to force video to the external display. Theoretically this can be done at any time in the boot process & even while sitting at the log in screen or even desktop, but I have found sometimes it may be necessary to trigger Clamshell Mode during the early boot process by closing the lid of the laptop immediately (within a few seconds) after hearing the startup chime.

What is the highest version of macOS which has been installed on this laptop?

Is this laptop using the original Apple SSD or a different one? If a different one, is it an Apple SSD or a third party SSD? The reason this may be important is that Apple hardware & macOS sometimes has some odd behaviors with unexpected hardware installed.

If macOS 12.x Monterey has been installed on this laptop at some point (installed is critical as well as having run the installer on this laptop specifically).....just want to make sure whether the system firmware is at the latest version.....if not, then installing a newer version of macOS (up to Monterey) would update the firmware.

Otherwise if an SMC Reset and PRAM Reset (hold the PRAM Reset for at least three chimes) don't resolve it, then most likely there is a hardware issue of some sort with the Logic Board. Just make sure to disconnect all external devices.