The current pre-release of the client ("pioneer" in the version) is only compatible to itself. So you can only play with other testers. Please be aware!
Do you have a stable connection?
You can try to ping google for a minute or so and see if you got any spikes or timeouts.
https://i.imgur.com/YyJPxc1.png
For testing purpose:
Disable any security software
Try a VPN from a different country
