I am having the same issue on SonarQube 8.4.1 (build 35646), EE.
What happened in my case was it started with a project that failed consistently running the background tasks after successful analysis.
The error in that case was something like:
Project or branch in report (myProjectKey::myBranchName) does not match the project or branch under which it was submitted (myProjectKey:::BRANCH:master)
although I no longer have the exact error message because the entry no longer shows in the background tasks UI, so I may have be off by a colon or the name “master,” but that was the gist of it.
I deleted the project from the Administration UI, which succeeded.
Afterward all my scans fail with:
Compute Engine task main component key is null. Project with UUID myProjectUuid must have been deleted since report was uploaded. Can not proceed.
And now this happens consistently. Even if I delete the project (which seems to succeed as before) and rescan, it keeps happening.
What does it mean for a project to be partially deleted, and how can I fully clean it up?