I’ve got a similar problem. Got some downloaded prezis on a usb stick. They worked like a charm for years now but suddenly they won’t open anymore. Have tried to download my prezi on a new memory stick: same problem. Tried a simple test prezi (no images, short filename etc.): same again.
Strange enough, the problem only seems to occur on my Windows 10 computer. And when i open de prezi on the pc itself it works just fine. Only when i download, copy or extract the portable prezi on a stick it won’t play. Have tried it also on another windows 10 pc: same problem.
Could you please help me out?