Well I believe the issue is something about the update is causing our programs to see yousician as malware. I am willing to bet most of us are using "avast virus protection" on our PCs. I went into my virus chest and restored the program with an exception to allow yousician going forward.
The program is working on my PC again
If you just keep downloading without putting the exception your PC's virus program thinks it's getting attacked and will deny program access.
Hope this helps, and there isn't a nasty virus in the app causing me to mess up my computer lol