Login redirects me back to homepage as if i didn't log in

[frankie.]

When users log into the forum they get the redirect page:

"Thank you for logging in, user" but then it redirects back to the home page as if they weren't logged in.

but if you click on the top left logo then it loads as if you're logged in.

I recently upgraded to version 4.1.4 from 3.8.x

I didn't have this problem before.

any ideas? I can create a test account.