Wireguard VPN Blocking https://addons.mozilla.org
I disabled uBlock. I cleared my cache, cookies, etc. I unchecked "Enable DNS". I reinstalled 77.0.1 over my current installation. No luck.
When I disable the VPN on my router, I CAN access https://addons.mozilla.org. I use Mullvad Wireguard VPN on my GL.iNet GL-AR750S.
Before the FireFox update, I did not have this issue. I don't know how this will effect my installed addons. I doubt they will auto-update unless I somehow whitelist the url to bypass my VPN.
I will pass the issue on to Mullvad, as well.