All menus once left open when you minimize Masterplan [and then restore the window] will disappear and can't be opened again [via 'View'] 

- GIF - Imgur

Temporary fix would be to close all menus before you minimize the Masterplan app.

Thanks again for your work!

Yeah I ran into this many, many times in one session. Troublesome issue to deal with when trying to do a client spec

Sorry about that! I thought I resolved this, but that wasn't the case. The issue should be fixed now in the update I just pushed out. Thanks for reporting!

I can confirm it's fixed on my computer. Thanks for your quick response!