None of my admin accounts are sudo users
It sounds like your employer has disabled using sudo commands from any admin account, instead opting to include only specific users. This would mean only the employer's admin account would be able to use sudo. If you no longer have access to this account, you could boot into Single User Mode and run the visudo command to fix it. If they didn't remove the user from the sudoers list, you could also make a new admin account with the same shortname.