IOS SSL VPN
Can you post your config so we can review it?
What client browser and OS are you using to test?
Are you using a self-signed certificate or one from a trusted CA?
My first thought is the browser does not trust self-signed certificates. Try temporarily disabling the security settings on the browser and test the connection again. Then be sure to re-enable the security settings. If the connection works, then the issue is the self-signed cert.
Alternatively, if you have Certificate Authority (CA) server setup on your network, you can generate a cert and import it on the router. Or you can always buy an official cert if this is going to be on the Internet. Either of these methods should circumvent the security setting issue in the browser if the CA is trusted in your browser settings.
Let me know the results of trying these suggestions. If it still doesn't work, I'll need more information such as full config files (minus the passwords) and browser settings.
Another thought is to try regenerating the cert on the router. I've had issues with ssh not working due to bad certs.
I'll see if I can set this up in a lab and let you know the results in a few days.