I downloaded 8.5.0 to try the new "minimum due" feature and see if it fixed another problem I had. After tinkering, it didn't address the second problem[1], so I decided to restore from backup from before I started tinkering. It asked me to reset the Quicken Cloud file, so that I had to re-link my accounts and eBills, but none of my accounts will link to eBill, even though it says that linking was successful.
This is affecting all my accounts that were previously linked.
It says the eBill is linked:
but then the status remains unlinked:
There doesn't appear to be any errors in any of the log files.
[1] https://community.quicken.com/discussion/7966047/ebills-issue-1#latest