Offering to co-maintain Custom Text

The procedure for How to become project owner, maintainer, or co-maintainer → says:

When the project is covered by Drupal's security advisory policy, you need to have permission to opt into security advisory coverage, or the offer must be approved by the project's owner. The site moderators will not add as owner, maintainer, or co-maintainer a user who cannot opt projects into security coverage. See Apply for permission to opt into security advisory coverage → for details on how to obtain that permission.

This project is opted into security coverage, and you do not have permission to opt into security coverage. Moving it back to Custom Text to be processed by the project's owner.