YoWindow for Windows and Mac is not able to function without Flash. If you uninstall Flash from your computer, YoWindow will not be able to work.
We are sorry. Unfortunately, the situation is beyond our control.
Anyway, right now we are working on new YoWindow version that will not depend on Flash. We hope to release the new version by the end of 2021. If you own YoWindow license key it will unlock the new version. For the time being you are welcome to run YoWindow on iOS and Android.

Here's a workaround
Google for the old version of "ADOBE FLASH PLAYER" v29.0.0.96
Install it.
Flash should be working fine with no problems.