Have you tried a different hot key? Colab's editor binds ⌃E to "move cursor to end of line", and web apps have a habit of grabbing keystrokes before KM gets to see them.
Not necessarily a solution, but it'll help define the problem.
...you can easily test "activation" -- if the Group is active the Group's palette will be on screen, if it isn't it won't be.
For me, following your instructions above, the Group is active when the Colab PWA is frontmost. And the ⌃⌥⌘U hot key combo works fine. So you'll have to dig deeper on your own setup to solve this.
That sounds like a "translocation" issue -- the app being translocated (for security) when run from your home folder but not when run from /Applications.
Interesting that it doesn't happen for me (running macOS 15.1.1 on this machine).