The system is Fedora 35, the Thunderbird level is 91.1. This is an upgrade from FC32. I was unable to upgrade using the normal Fedora upgrade process so I created a new install into a dedicated root directory. Normally the home directory is a separate partition. In order to have the user ids and group ids match theose in the home partition new users were created to match those ids in the home directory. When this was completed the new install /home was deleted and the fc32 home partition mounted on /home. Additionally /etc/fstab was updated to support mounting on reboot. Evetything worked as intended. All directories and files were accessable. Thunderbird e-mail config and e-mail history came across as intended. The only thing that did not come across were the calendar entries and calendar functions. Additionall the calendar is locked out, no new entries can be created. All the options in the options bar are greyed out. There are no calendar options in e-mails. The calendar appears but is totally 'dead' for a better description. The above is also true for tasks. I assume this is a residural from brining the calendar through multiple levels without going thourgh level upgrade scripts. I have removed lightening and I have removed and installed thunderbird; neither of these had any effect. A vialble option is to erase the calendar entries from .mozilla and start fresh. I am assuming this would rebuild the canledar on restart. I am uncertain how to do this. I do not want to erase the e-mail history.