Check first what URL you are using:
cd /path/to/local/repo
git remote -v
If it is an HTTPS URL, check what credential helper you are using
git config credential.helper
xxx
(For instance, manager or manager-core)
Then check what credential is attached to dev.azure.com, the server part of your remote URL:
printf "host=dev.azure.com\nprotocol=https" | git credential-xxx get
Replace xxx with the name of the credential helper for the previous step.
This work even in a Windows CMD, provided your %PATH% has C:\Program Files\Git\usr\bin and C:\Program Files\Git\mingw64\libexec\git-core
If your credential is not stored, you can register it again with git credential-xxx store:
printf "username=<you>\npassword=<token>\nhost=dev.azure.com\nprotocol=https" | git credential-xxx store
Replace <you> with your DevOps username, and <token> with an Azure PAT (Personal Access token).