A couple things to check...
1. Do you see anything of interest in CPPM->Monitoring->Even Viewer?
2. In CPG, Under the Guest Self Reg page you are using, check the NAS Login settings. They should be set to Aruba. If you ever changed your certificate on your controller, then you will need to change the IP Address listed from securelogin.arubanetworks.com to whatever the cert was that you put on your controller. Or for testing with a single controller, you could set this to the IP address of the controller on the Guest VLAN.