You can use this page to diagnose some (but sadly not all) connectivity problems.
If Symmetric NAT is found then your router is not ideal. You will only be able to join rooms hosted by people without Symmetric NAT. Some routers have an option to change how NAT works, otherwise replacing the router might be necesary.
If no srflx or host candidates are found then it's possible that webrtc is being blocked by your browser, in this case try disabling extensions or try running this test with a different browser.
Srflx candidates found:
Host candidates found:
Symmetric NAT found: