Okay, but how
are you trying to do this? Are you trying to do this from the web client? Android? Email client?
When I asked for specificity I didn't mean "type everyithing again but with less words."
If you don't know how to explain more clearly, try answering to this questions:
- Is there anything different about this account you are trying to add?
- Is this a regular account or an account managed by an organization?
- If it's not a regular account, have you tried to find out if there are any limitations to this type of account?
- Have you tried searching for your problem somewhere else? (for example: https://support.google.com/mail/thread/8805971?hl=en)
- Did you try to solve the problem on your own first? If so, what did you try already?