Is your M3U link active? It’s simple to check.
Go in your email and find the activation email. Click the M3U link - a .m3u file should be downloading now. If a blank page is shown after you press the URL, the account is not valid or expired.
Alternatively, select and copy: CTRL+C your M3U link, and paste CTRL+V in the address bar of your browser. Then press ENTER.
Test in VLC using copy: CTRL+C & paste: CTRL+V to eliminate the risk to make a typo in your URL.
Find the tutorial here: VLC Player (Mac, Windows)