First try using a different browser. We recommend using the latest version of Google Chrome, Mozilla Firefox, Apple Safari or Microsoft Edge (after the Summer 2020 update). Make sure you disable all of its extensions first.
If you have AVG antivirus, please disable the Link Checker feature and reboot your computer. That feature of AVG is very intrusive and kills timing-sensitive Javascript procedures, like the backup procedure.
If this doesn't work, try disabling any antivirus/firewall/Internet security application. Windows Defender is safe to leave enabled.
If nothing of the above works, please try using a different PC, ideally connected to the Internet through a different ISP. We had many cases where the PC setup was broken and using a different computer did the trick.
If the above information doesn't help, please go back to the previous page and continue reading.