Unsure if this was ever solved, but just for other people's reference:
I was having this exact error and finally figured it out. I would get this ModuleNotFoundError: No module named 'panel' error no matter what I did - and I was setting up Minian on a completely new computer. I only just noticed today that for some reason, panel would be saved in site-packages in my main minian environment folder. Not in Lib/site-packages where everything else was. I just moved it into Lib/site-packages and everything has worked since then!