Hello,
we officially do not support beta versions of MacOS, but we try to fix all we can during our normal release cycle so that it works. Unfortunately the fix did not get into the last release of MacAV. When the next version gets out, it should be working. Saying this, the MacOS beta contains at least one bug that impacts MacAV, hopefully Apple will fix it before the release.
Kind regards,
Ondrej Kolacek