Hello,
We've fixed this issue but posting here in case others run into it...
After updating Wwise from 2019.1.4 to 2019.2.1 in our Unity project with the latest integration we found that our custom plugins falied to link on iOS and Android. We tracked the problem down to a faulty path.
var projectPath = AkWwiseEditorSettings.WwiseProjectAbsolutePath; (Assets/Wwise/Editor/WwiseSetupWizard/AkPluginActivator.cs:696)
returns the full path to the Wwise project including the project file name (.wproj). As a result the path the PluginActivator builds to PluginInfo.xml is invalid. If PluginInfo is not found at that location the PluginActivator searches in StreamingAssets. This may mask the issue for many projects but in ours we don't keep any Wwise files in StreamingAssets so both attempts to locate PluginInfo.xml fail.
We fixed it by changing the line above to:
var projectPath = System.IO.Path.GetDirectoryName(AkWwiseEditorSettings.WwiseProjectAbsolutePath);