SAP Portal to SRM SSO not working for the first time. It works for the second time

Hi Experts,

We have configured SSO from SAP EP to SAP SRM system. Below points are already checked.

1) Certificates are exchanged between SAP Portal & SAP SRM

2) Trust Established to SAP SRM from SAP Portal

3) System Object for SAP SRM Created and Connection Test is passed

Now, while perform the testing of SSO from System Admin --> Support --> Test and Configuration Tools --> choose transaction --> Selected SRM system alias and mentioned common t.code (ex: SMEN) and clicked on Submit

We ended up with netweaver logon screen. If we close that and repeat the same steps for the second time, SSO is working. It means, without asking user id and password, SAP SRM Home Page appeared.

Kindly help me to identify this issue. What is disturbing the SSO for the first attempt ? and how its working on the second attempt? Kindly provide some light on this issue.

Thanks,

Gowtham