what you see in server.log file? is IAM loading sequence (around 36 I guess) successful? Sometimes policy server takes time reading policy store and if WAM UI service is brought up during that time, Policy server will not serve request.
1) Wait for policy server to be ready (it will show message in smps.log that it is ready)
2) Stop WAM UI service completely
3) Start WAM UI server and watch server.log. When you see message all startup sequences are completed, try to login. If that does not work, you might want to enable access logs and post server.log for further troubleshooting.