I suspended an account on my server but when I try to unsuspend it it won't work

any idea I'm using CPANEL/WHM

If you are a reseller, try asking your web host for help. Sometimes cpanel gets "stuck" and needs a kick. ;)

If you are root, then try asking in the cpanel.net forums. There's just so many things that might be wrong it's hard to know where to start.

what message appears to you even?
Make sure it's not listed within Inactive Domain Names in your WHM settings. Are you root?

What is the error message you are getting now? Sometimes you tend to get 403 message after unsuspend in wHM. After you usnspend the account in in WHM chmod the public_html folder to 755.