We have a drupal site running on pantheon server. We are facing issue with login in site.
We are able to login in site, but whenever we open any other page except "user" page, it shows that you are not logged in. Again we open user page, it shows as logged in user.
We can not determine what is the issue.
Please help us in this issue.
There may be caching issue on server side. Try to disable all caching, and disable or clear varnish cache.
Then use Drush rebuild registry command from terminal
drush rr
You can find more information here. How to execute Drush commands on Pantheon.
If above solution not works then try to debugging cache on Pantheon