It's odd that it has stopped after a couple of days. I am sure that you've double-checked the audio settings.
To make sure that everything-else is working OK, can you try AT5 plug-in in a DAW?
As this is primarily a user to user forum, someone-else may chip in [#]. Meanwhile, the best thing to do is
check the FAQs, via here. If they do not resolve the issue, there is a link at the top to the Technical Support form, for some one to one investigation and help. Response time is usually within 2 working days (US (East Coast) Business hours, generally), but in the current circumstances please allow some more time.
[#] But please remember that the same symptoms do not necessarily mean the same problem.
And, to help others who run into a similar problem, please let us know what you did to resolve the problem. Please do not quote directly any correspondence from Support, as that may apply only to your particular circumstances.