I can't install the upgrade on macOS Catalina

Hello there, Community.

I have an Imac late 2015 (Retina 5k, 27-inch)

3.2GHz Quad-core Intel Core i5

Since I got Catalina, I was not able to upgrade the computer to any of the later updates.

It just doesn't do it. No matter what I try.

I got space and everything.

This is what it does:

It starts to install, and it shows the bar through the screen advancing.

Then, it stops, and it will do the same thing again, never installing the upgrade.

I have never really cared to much to pursue the upgrade, because the computer runs great.

But some later apps that I use for work, like Final Cut Pro, won't install or work if the system is not upgraded.

Any help? I would appreciate it, I need to go back to work.

Thank you so much!