When uploading Projects to a target PWA using Upload Projects from FPP Files wizard, FluentBooks failed to upload the Project and the following error in FluentBooks log file occurred:
(Exception) ServerException: Cannot invoke method or retrieve property from null object. Object returned by the following call stack is null. "GetByGuid" Projects new Microsoft.ProjectServer.PSContext()
Such an error occurs in case a Project already exists in a target PWA as a draft or archived project. For some reason, it was not published during the initial upload/creation.
Navigate to PWA Settings -> Queue and Database Administration -> Delete Enterprise Objects. Please verify if the Project has the status 'Working' in the section 'Version' and if so, please try to delete it and then upload this Project via FluentBooks once again.
To check if the Project is archived, click on the 'Delete archived projects' radio button. Please try to delete it and then upload this Project via FluentBooks once again.