Editor has an annoying habit to lose a link to Unity Services:
If it happens, is impossible to compile and run project even in Editor. It is frustrating. It ruins all productivity. If it happens, while I have trouble to access internet, I can’t do workaround and relink my project. In this case I can’t do anything.
So, please, make it possible to compile and run the project, even if Unity IAP is disabled.
Yes, there is currently a bug when you use the preference “Load previous project on startup”
If you make sure to leave that box unchecked, your project will stay linked when you close and open your project. (You will have to select it from your project list, but it will be the first one in the list.)
I apologize for any inconvenience this issue has caused.
We have had some users report success when signing out of the Editor and signing back in. Of course, this isn’t something you should need to do often.
Whenever this happens, can you submit a bug report in the engine (Help → Report a bug)? Please provide as much detail as you can. Someone from our QA team should contact you afterwards and hopefully that conversation will lead to this a resolution to this issue.
It looks like that case was marked as a duplicate of 864152 and that case was marked as resolved in 5.6. So this bug should be fixed in the next version (and likely the current 5.6 beta). If you find that’s not the case, please message me and I will reach out to our QA team for more information.