Logon ticket error in ep 7.31 after upgrade

we have upgraded portal from 7.0 to 7.32.

Also HCM package is updated to EHP6.

After upgrade, we are getting portal runtime error for all iviews.

NWA log says: com.sapportals.portal.appintegrator.ApplicationIntegratorException: com.sap.security.api.umap.NoLogonDataAvailableException: No logon ticket available.

at com.sapportals.portal.appintegrator.accessor.ume.UMEAccessor.getTicket(UMEAccessor.java:99)
...

What can be the reason for this error?

Thanks in advance.