I can imagine it is frustrating.
To be honest, it could be something to do with either AT4 or the interface being old and not being compatible with the new Mac CPU or OS.
As this is a user-to-user forum and not direct to IKM support, in case no one else chimes in here with advice or a solution the best thing to do is check the FAQs, via
https://www.ikmultimedia.com/contact-su ... ck=QUICKSWIf these do not resolve the issue, there is a link to the Technical Support form at the top of the Search FAQs page, for direct help from Official IK Support. They endeavour to reply within 2 working days, but obviously considering the current situation things may take longer than usual.
And, to help others who run into a similar problem, please let us know what you did to resolve the issues, but without directly quoting any correspondence from official support.