Today, a colleague couldn't do docker login for an internal registry. Constantly got an error which just said "unauthorized".
The password couldn't be the problem, because you actually generate a token on the registry webpage, so we tried all the different ways to spell his username (uppercase, lowercase, e-mail address) and tried different URLs for specifying the registry, tried toggling the VPN, a reboot etc., even though we knew what should work, because the login worked for me.

Eventually, we gave up and figured there must be some permission problem in the registry. Ten minutes later, he tells me that it works, without doing anything different. Now I'm wondering, if the IT saw our desperate login attempts and quickly fixed the problem. 🫠