Need to remove the user who is currently tagged as org and site admin only.
This user is tagged as org and site admin.
Have you managed to resolve this? To avoid users locking themselves out, organisations must always have at least a admin. If this user has left your company and their (Atlassian) account is inactive, then Atlassian should be able to help.
If the user is still active, then s/he will need to transfer the organization admin rights to another user first.