Mac mini M4 2nd external display (portable monitor via USB-C) not working

My mac mini m4 was working perfectly fine with 2 monitors before - one is my TV connected via an HDMI to usb-c adapter into the mac mini, and one portable monitor connected to the mac mini via a usb-c to usb-c cable, which also powers the portable monitor.

The cable for the portable monitor does support display port which should work with thunderbolt 4 plug at the back of the mac mini m4. Also, the setup has been working for about 1 month, but then it suddenly stopped working yesterday - the only events happening recently that I can remember was a power cut that happened while the mac mini was on and connected to both displays.

Now, the mac mini m4 only connects to the TV while both displays are plugged in. On startup, both display screens up, with one having the login screen, but the cursor only works on one of them. After login in, only the TV display works, and the portable monitor just freezes.

I have tested the portable monitor and the cables with a window laptop and it worked just fine. Also, connecting the mac mini with JUST one display either the TV or the portable monitor also works - they just don't work when connected together. It's perplexes me that my setup has been working for over a month and now it suddenly stops working.

[Re-Titled by Moderator]