Have the same issue since today's update. There is an error popping up in game, that ascension.dll failed to load. Tried everything described here - but no luck so far.
And it looks like the file is not touched by the Ascension launcher in any way. I renamed the file to ".dll_OLD" to test if it will be re-created or downloaded again. But no. Nothing happens even when you repair or re-install the launcher.
After 2 hours of ducking with the client in all possible combinations: just took the whole Ascension client folder from my wife... and it's working now. She has the same Windows version as me.
So, the problem is not in PC configuration or firewall/antivirus rules, but in the client itself. I also pasted all my backed up folders "Cache", "WTF", "Interface" win all the addons inside.. no issues so far.