Hello,
I moved to the latest version of the engine (5.6.1) and using version 2.03.09 of the Unreal Integration prevents compilation. It is related to a mistype in the generated FMODCallbackHandler source file
I found a solution in replacing the plugin’s Intermediate folder with the downloaded copy. It may be due to the fact that the mistake exists in the Linux version of the plugin (I have a Windows host but package for Linux).