The free Linux plan on CircleCI has 1,000 minutes of build time available per month: https://circleci.com/pricing
When this limit is hit, you may see the following message on builds:
Your build was not run - reason code (:org-over-credit-limit)
Your monthly cycle is based on the date the org was created on CircleCI (not necessarily 1st of the month).
You can upgrade to a paid plan to remove the build minutes limitation.
If you’re building an Open Source project you can use the Open Source plan which will remove the minutes limitation. This can be enabled in: Project Settings > Advanced Settings > Free and Open Source.
The limit is to prevent abuse of the platform so we can provide the best service for everyone.