Ok, I'm not the expert on everything, but here's my suggestion. It appears there is an upgrade 'stuck' in the system. I would first do a backup of profile, then uninstall thunderbird, reboot the PC, and then install the update. you can backup the profile by - exiting thunderbird - copying c:\users\<yourid>\appdata\roaming\thunderbird to somewhere else

If, for some unforeseen reason, the update starts with a fresh profile, just exit thunderbird and copy the backed-up thunderbird folder to c:\users\<yourid>\appdata\roaming to overwrite the existing profile.