I experienced similar problems and I finally had one Avalara representative ask me if I tried going back to the older .95 version. After I uninstalled.99 version and reinstalled.95 version, Avatax began working properly again. You also have to make sure you decline or tell it “no” to the certificate “add on” under preferences. You only one want integration of Avatax under “apps” and you can verify that it is the .95 version of Avatax