I know this is three years late, but I just encountered the same thing...

After a lot of investigation and debugging, what eventually fixed Monkeyflow was just deleting its cache folder (which lives at {system drive]/Users/[username]/AppData/Local/Temp/monkeyflow_cache) and restarting Media Monkey.

Hopefully this helps someone else who encounters the Monkeyflow white screen in the future.

Hi everyone. I have recently updated my MM and took with me the Addon MonkeyFlow. what used to work like a dream in now a mystery! I installed the Add on into the Auto Folder and unzipped it. I then ran MM as admin. The programme opened fine and Monkey Flow appeared on the "view" tag. However there is just a white box in the play area. I can enlarge it etc but there is no artwork, no words and no menu to change the settings. I have tried all the usual things and nothing seems to work. I seem to remember before that I double clicked on the Monkey Flow icon. Doing that now gets no response. It used to say initializing Monkey Flow but now - nothing - Any ideas? thanks very much