SSO via cookie not working after upgrade to 4.4.1

After 4.0.4 (+sec patches) to 4.4.1 upgrade SSO via cookies not working anymore. Config is the same, all plugin files deleted.

Connection to mysql is working (stunnel to other server is listening here). RT login via LDAP working too.

Server is on server.domain.tld, cookie from browser:

Name: appAccess
Content: …
Domain: .domain.tld
Path: /
Send For: Any type of connection
Expires: today + 1d

Content is the same like session_id for my username in mysql.

Have some hints?