Forum for bugs or customer concerns
It's not an idea, it's a bug. Please provide a forum for bugs - this sort of post should not clutter up ideas and suggestion!
I just upgraded from free to pro. I had 2 projects in the free version. One never showed the thumbnail and didn't after upgrade either.
We appreciate your suggestion and made a small edit to it for better understanding. I believe one of our support is already helping you out on how to switch from free to pro version.
If you need further assistance, please email us and we will be happy to assist you.