gitlab one of the most used GIT servers , that can be installed on premise can generate a problem about key expiration if not constantly update .
Err:4 https://packages.gitlab.com/gitlab/gitlab-ce/debian buster InRelease
The following signatures were invalid: EXPKEYSIG 3F01618A51312F3F GitLab B.V. (package repository signing key)
<packages@gitlab.com>
Reading package lists... Done
W: An error occurred during the signature verification.
The repository is not updated and the previous index files will be used.
GPG error: https://packages.gitlab.com/gitlab/gitlab-ce/debian buster InRelease:
The following signatures were invalid: EXPKEYSIG 3F01618A51312F3F GitLab B.V. (package repository signing key)
<packages@gitlab.com>
this can be solved by installing keys as always , or just reRun the installer script that will do the job by itselfs.