This guide might help you if you are having trouble connecting to rooms.
The game is peer to peer which means you connect directly to the owner of the room. This however, requires that both player's routers cooperate and unfortunately some routers will prevent the connection from being established.
If you normally use Chrome, try with Firefox. If you use Firefox then try with Chrome.
If your home network has more than one router between the internet cable and your computer then try connecting your computer to the first router. The less routers the better.
Some routers allow you to configure the NAT behaviour, the name of this setting can vary between routers.
However, most routers don't have this option so don't get your hopes up.
Look for a setting that lets you pick between some of these options:
If you find it, you want to select full-cone or restricted-cone. You definitely want to avoid symmetric-nat and NAPT.
For this you will need to set up your computer to use a static ip address instead of dynamically obtaining one with DHCP.
Then you'll want to add a port forwarding rule to your router so that all UDP messages in the port range 49152 to 65535 are forwarded to your computer's static ip address.
You can find detailed instructions of how to port forward in portforward.com
Enabling DMZ and pointing it towards your computer can improve the symmetric nat situation. For this you will need to set up your computer to use a static ip address instead of dynamically obtaining one with DHCP.
Keep in mind that DMZ makes your computer more accessible to the internet which is generally bad for security.
If you are fine with having a single computer connected to the router, then setting it as bridge will get rid of NAT and probably improve the situation.
If all else fails then you can try replacing the router for a different model. Sadly the NAT mode is usually not advertised so there's no good way to know if the router works properly without trying it.