AdBlock doesn't appear to be filtering out ads from subscriptions at all. Oftentimes subscriptions display "(Error: Cannot load subscription!)" after their title either when initially adding them, or after attempting to update subscriptions. Whether the error is displayed or not though, there appears to be no filtering happening based on subscriptions; individual custom rules work, but not subscriptions.
Please post terminal output and what subscriptions you are trying to add/update. Most likely it fails to download it due to url being no longer available.
Created attachment 113622 [details] Terminal output
I am attempting to add EasyList (from URL: https://easylist.to/easylist/easylist.txt) and Peter Lowe's List (from URL: http://pgl.yoyo.org/adservers/serverlist.php?hostformat=adblockplus&mimetype=plaintext)
Looks like Qt (QNetworkAccessManager) thinks you are offline, not sure why though.
Ah, ok that was the problem. QNetworkAccessManager was attempting to connect to a different network interface that I once used months ago, but is no longer installed. Everything seemed to be working though, so I never noticed. Clearing that up fixed the AdBlock issue. Sorry to bother you with that.
Thanks for the update; changing status.