Developer here at AVAIL – the underlying issue was due to a third-party assembly that both Dynamo and the AVAIL Browser for Revit utilize. It appears that if an assembly with the same name is used by two separate addins, Revit only loads the current or newest version that it encounters during the startup process. In this instance, the AVAIL Browser for Revit’s version of the assembly in question was loaded first, and had ignored Dynamo’s version.
A new version of the AVAIL Browser for Revit (v3.2.4.0) is available to download that addresses this issue. If others are experiencing this as well, you can download this version by going to https://getavail.com/download