How to reactivate a user when I'm not seeing a reactivate button?

[Pamela De Costa]

A guest was deactivated and I'm not able to reactivate the user. There is no reactivate button against the person's name on the members list and if I try to add them back to the workspace or board, I get a message that the user is not a managed Enterprise member or do not have an allowed email domain. 

[Nic Brough -Adaptavist-]

Welcome to the Atlassian Community!

This is what it says it is - you have an old user account that is no longer valid for your system.  You cant re-enable an account that can't be used on your system.

[Pamela De Costa]

I'm not even sure why the account was deactivated and the user's email address I'm trying to reactivate is valid/ current. Still unclear on how I add back the person if the email address is coming up as invalid. 

[Nic Brough -Adaptavist-]

I would want to check that the account is still working first.  Ideally, get them to log into it at https://id.atlassian.com and check everything is looking ok.

Then I would want to check how your Trello is configured to let people into it - it sounds like you have got it set up to only allow people with accounts on certain domains in.