An administrator of a website or network may decide to suspend a user, preventing them access for a period of time. Is there an antonym of 'suspend' meaning to re-allow that user access?
I would use reinstate:
to put back or establish again, as in a former position or state: to reinstate the ousted chairman.
As a sysadmin the word we usually use is just 'activate'. e.g your account was suspended because the password expired, I have just activated it for you. It may not be grammatically correct but that is usually the on-screen option, button or command used in the software to do what you are saying.
(Or if you want to keep looking for other words, the origin of 'account' comes from mainframes when you had to pay to use it and your account was the amount of money you had put in. When you ran out of money your account was suspended, just like business accounting systems would do to customers. Try looking at business accounting terms if you want more ideas )