I never got it to work. I'll try again since it's been updated.
Which everdrive/Nintendo models are you trying to use SynthNes with?
NES-001 and an Everdrive N8 Pro. checking the O.S. version... 2.11 from December 2021.
What behavior are you seeing? Does anything happen when you click the deploy button with the star? Have you tried using a different USB cable?