When a repository is in 'read-only' mode, it means that nothing can be written to the repository.

There are a few reasons why a repository is in 'read-only' mode:

• If a Workspace is on the free plan, this workspace is limited to 5 users. For annual paid plans, the user limit will depend on your subscription.  If the number of users with access to the workspace exceeds these limits, all private repositories in this workspace will automatically be set to 'read-only' mode. The workspace owner will need to remove excess users or update their workspace plan to be able to add more users. For more information, see Plans and billing and for troubleshooting please see this article.

• You have exceeded the 4GB repository limit for the repository and cannot perform any further commits to this repository as a result - an error will be displayed in your GIT client informing you of this. To resolve the problem will need to either raise a support ticket or a community support ticket for further assistance. 

• We are upgrading our storage segments and temporarily can't accept new data.

• Atlassian が変更をロールアウトしており、一時的に書き込みが制限されている。

• Performing maintenance on the repository, such as running the garbage collector (GC) to clean up dangling commits and reducing the size of the repository.

Read-only mode usually only lasts for a few minutes, so if your repository has been marked read-only, try it again in a little while.