Why is my mouse's right-click not working on macOS 15.5?

Give this a try: boot into Safe Mode according to How to use safe mode on your Mac and test to see if the problem persists. Reboot normally and test again.

NOTE 1: Safe Mode boot can take up to 3 - 5 minutes as it's doing the following; 

• Verifies your startup disk and attempts to repair directory issues, if needed

• Loads only required kernel extensions (prevents 3rd party kernel/extensions from loading)

• Prevents Startup Items and Login Items from opening automatically

• Disables user-installed fonts 

• Deletes font caches, kernel cache, and other system cache files

NOTE 2: if you have a wireless keyboard with rechargeable batteries connect it with its charging cable before booting into Safe Mode. This makes it act as a wired keyboard as will insure a successful boot into Safe Mode.

Have you installed and run any "cleaning", "optimizing", "speed-up", anti-virus or VPN apps on your Mac?

I had a similar problem. I upgraded two days ago, and today I found my Magic Mouse wasn't maintaining 'mouse-down' during menu selections. It was also interfering with my changing file or folder names. Using a wired mouse instead (I always keep a spare mouse to hand!) made no difference, so it clearly wasn't the mouse! I tried a few solutions, but none worked, so I took the 'drastic' step of re-installing MacOS 15.5 using Recovery Mode. That worked! My mice are now functioning normally. I can only assume it has something to do with the upgrade package, and not OS 15.5 itself, but I am happy to be corrected on that! And very happy that my iMac M1 is working well again.

I had a similar problem. I upgraded two days ago, and today I found my Magic Mouse wasn't maintaining 'mouse-down' during menu selections. It was also interfering with my changing file or folder names. Using a wired mouse instead (I always keep a spare mouse to hand!) made no difference, so it clearly wasn't the mouse! I tried a few solutions, but none worked, so I took the 'drastic' step of re-installing MacOS 15.5 using Recovery Mode. That worked! My mice are now functioning normally. I can only assume it has something to do with the upgrade package, and not OS 15.5 itself, but I am happy to be corrected on that! And very happy that my iMac M1 is working well again.

Barney-15E wrote:

There is no right click in macOS. There isn’t even a left click. There is only one button on the mouse so it’s just a mouse click. You can get a secondary click by holding down the control key when you click the mouse.

Not sure what you are saying. You can certainly do a "right click" with an Apple Mouse without holding the control key.

Just to add, the secondary click is the same as a right click.

dialabrain wrote:

Yes, the "gesture" is "Click Right Side".

https://discussions.apple.com/content/attachment/da562c63-bc31-44ce-bda6-83842a7b9dac

Where does it say click the right mouse button?

Neither the Magic Mouse nor the Magic Trackpad has any buttons. It's all just touch sensors. At best, they both are one button. Touching the one "button" in the appropriate way generates various functions, one of which is Secondary Click.

dialabrain wrote:

Barney-15E wrote:

There is no right click in macOS. There isn’t even a left click. There is only one button on the mouse so it’s just a mouse click. You can get a secondary click by holding down the control key when you click the mouse.

Not sure what you are saying. You can certainly do a "right click" with an Apple Mouse without holding the control key.

You should continue reading. It's right there on the very next sentence.

Here are the instructions for a Trackpad--I don't have a Magic Mouse

Just to add, the secondary click is the same as a right click.

And, that's covered in the next sentence.

dialabrain wrote:

Barney-15E wrote:

-And, that's covered in the next sentence.

Sorry, I don't see any sentence where you say you can do a right/secondary click with an Apple Mouse, without holding the control key.

sungyle wrote:

Digging deeper, I discovered this issue has been reported as far back as 4 years ago — and the official response from Apple at the time was essentially: "Just use Control-Click.”

Just to add, that's not possible seeing Sequoia hasn't not been available for four years.

Make sure System Settings > Mouse > Secondary click is set to "Click Right Side".

There is no right click in macOS. There isn’t even a left click. There is only one button on the mouse so it’s just a mouse click. You can get a secondary click by holding down the control key when you click the mouse.There are gestures, you can perform on a magic mouse or a magic trackpad to generate a secondary click.Many not an apple mice come with more than one button and if they are HID compliant macOS will recognize a click on the right button as a secondary click and I’ll even recognize the middle button if there is one and the software you’re using recognizes it.

I have a TechNET Bluetooth mouse that has two buttons a scroll wheel button

All of those are natively recognized by macOS.

Since it “no longer“ works,I would assume that you are running software that makes the mouse work probably enabling more than those three buttons, and that software no longer works with that version of sequoia.

Old toad’s troubleshooting advice may help determine if it is software related as safe mode will disable third-party system modifications, and then the mouse should just work using standard HID compatibility

Barney-15E wrote:

Neither the Magic Mouse nor the Magic Trackpad has any buttons. It's all just touch sensors. At best, they both are one button. Touching the one "button" in the appropriate way generates various functions, one of which is Secondary Click.

No kidding? After three decades of using Apple Mice I've now learned there aren't separate buttons. Thank you.

Yes, the "gesture" is "Click Right Side".

FWIW. right-click works on all my Macs running Sequoia 15.5, just as it always has.

Barney-15E wrote:

-And, that's covered in the next sentence.

Sorry, I don't see any sentence where you say you can do a right/secondary click with an Apple Mouse, without holding the control key.

In other words, there is no need to hold the control key.