Ivy,
Fixed!
I decided to deactivate all plugins in my installation. I then tried to create a product in eStore and a membership level in eMember and it still didn’t work. So I instead deleted the eStore and eMember plugins completely, then re-uploaded them via FTP, re-activated them one at a time. I was able to successfully add a membership level and a product.
Not sure what the problem was but now all is fine.
Thanks,
Marcus