Builds return the error message "Blocked due to plan-no-user-seats-available" when the number of Active Users exceeds the allotted user count for the billing cycle. To unblock, users have to purchase seats then push a fresh commit to trigger a build. This is an issue for jobs that involve deploys, merges, etc. - e.g., you need to retrigger the build by redoing a GitHub merge, or some such...

CCI-I-1156