So I saw that Chaseplane totally stopped working and didn't show up in the toolbar. Nor were any of the keyboard shortcuts working, nothing at all. It was like it didn't exist. 

I won't bore you with the 30 min of troubleshooting I did, but now I have narrowed it down to one root cause, and this is completely reproducible on my machine. When I enable Justflight FS Traffic Module, Chaseplane doesn't load at all. When I remove Justflight, all is back to normal. 

Can someone else try and confirm? I want to know if this is restricted to my system, or else it's a general issue. Maybe I have some weird issue that's just me.

If it is a general issue, I'll inform Parallels42. 

I've had precisely the same experience as you. Activate FS Traffic in MSFS 2024 Addons Linker, load simulator, load a flight, and no ChasePlane icon appears in the simulator's taskbar. Disable it, and there it is, working. I've definitively determined that it is solely Just Flight FS Traffic causing this, and no other addon I'm using.