The sessions listed don’t describe how that process works, there is no polling. There’s been no recent changes to the authentication server and no other reports of issues with Google single sign-on. This may be an issue with IPv6, the domain will resolve to both IPv4 and IPv6. Run curl https://app4.pritunl.com/ip and curl https://app6.pritunl.com/ip to verify both IPv4 and IPv6 is working. If IPv6 is not working make sure it is fully disabled and there are no IPv6 DNS servers configured. This often happens when IPv6 is enabled on a VPC but a IPv6 gateway is never added to the routing table.
If you are seeing a stalled single sign-on connection request that can occur when the event system in the database is broken. Run sudo pritunl clear-message-cache.
Otherwise the issue is likely occurring on the client, it’s mostly the client that is interacting with the authentication requests. Open the Chrome developer tools and enable preserve log in the network tab.