There isnt enough information to answer this.
-Are you using clientless or anyconnect
-What error do you recieve
-What changes were made between when it was working and now that its not
-Try checking the output of "show run webvpn" and confirm that you have it enabled on the right interface.
-If you are starting from scratch and theres no ssl config, you could also go in through ASDM and run the SSL VPN wizard to create a new ssl config from scratch.
-heather
