Lightroom Masking

Which "Lightroom"- Classic or Cloud?

What Version Number?

Do you see the 'cog wheel' Masking tool icon?

Do you get the Masking panel when you click on the Masking icon?

Have you applied a Brush or Gadient to the area you want masked?

Have you changed the color of the overlay (eg. to white)?

Yes, screen-shots would help greatly!

Screencapture please

Masking is working fine for me. can you post your system information?

The red highlights can be turned on and off using the O key or the small checkbox saying "show overlay" under the masks.

Try to reset the Lightroom preferences.

https://www.lightroomqueen.com/how-do-i-reset-lightrooms-preferences/

It's recommended to backup your preferences before you reset the preferences to the default settings:

https://helpx.adobe.com/lightroom-classic/kb/preference-file-and-other-file-locations.html

If this doesn't help we need more informations about your environment.

Please provide also a copy of your 'System Info'. This can be get from the LrC Help > System Info menu item.

There's a copy button in the System Info dialog. Press this button and paste the info into your next forum post.