Are you manually setting up Thunderbird? I usually copy the hidden .thunderbird folder from my home folder on the pc to the home folder on a flash drive. It brings all the settings, all the addresses, and all the emails with it.
I must have missed something. I loaded a fresh copy of Linux Mint Cinnamon on an external USB disk drive, on a laptop, which seems to be running OK. I tried to copy the .thunderbird folder from the Linux setup on the laptop internal drive, where Thunderbird was working just fine, but when I access Thunderbird when booting from the external USB drive it wants me to go through the setup steps. What am I not doing correctly? Do I need to us a command in terminal mode that doesn't work on copy/paste? It put the copy in the .home folder as a "copy". Thanks.