Alright. I've gone into my registry and changed "LongPathsEnabled" value to 1 (to unlock the limit).

I still cannot open ACE with the same error. Could the problem be that there is a lock on my community folder (although I can still access it, and I'm the administrator)?

What path do I shorten and how?

What should I shorten it to? (what do I name it)

Can I just go into my file explorer and do it, or is there anything specific I need to do?

Where do I request a refund? I'm worried that changing it will stuff up everything.

I don't know if I can just change the underlined thing randomly or what.

Are you sure you don’t have a firewall or antivirus that could be blocking anything?

I have a folder named E:\WpSystem that has the same naming convention (S-1-5-21-407189478-2283906966-1042017628-1001) shown by Jxck.
That folder appeared after I installed MSFS onto the E: drive (E:\Flight Sims\Microsoft Flight Simulator). Although the E:\WpSystem folder is there, the 772 is installed in E:\Flight Sims\Microsoft Flight Simulator\Community\captainsim-aircraft-m772, and 773 is installed into E:\Flight Sims\Microsoft Flight Simulator\Community\captainsim-aircraft-m773, and all the necessary files are in their correct folders.
I can't understand why it would install in the wrong location.

Where is MSFS installed on your D: drive Jxck? Surely not in the D:\WpSystem folder, but if it is, I suggest you install it in E:\Microsoft Flight Simulator. To do that, you will need to uninstall MSFS, then create the Microsoft Flight Simulator folder on your E: drive, then install MSFS into that folder. I know uninstalling/reinstalling MSFS is a big task (I did this upon buying my second 2TB SSD (E: drive) back in May), but if that is the solution to your problem, it will be worth it in the end.