Hi, This might be the same problem as under discussion here. We think the problem may occur when loading the add-ons after a restart. See in particular the most recent posts on page 2 regarding use of TB "Safe Mode" (with add-ons disabled). This problem is also the subject of a bug filed here. If your problem turns out to be the same, please add any info you can to the bug discussion.

Ay up John . I suspect you may be correct in that following the advice of Paulo F produces what at least for now is a working version of Lightening . Thank you both . Closing and rebooting TB results in the same problem ie non function . At least we have a work round ! I will look at the bug report to see if I can offer any info .

Thanks for posting back. Are your two machines configured more or less the same? Have they both been through the same sequence of updates or did the laptop, which if I understand aright is still functioning correctly, skip some versions?

Any info would be useful here or preferably in the bug forum. Thanks

Good question . I accept W10 updates for both by default as they become available to that extent at least yes . As for TB updates no there has been a difference in that this machine the tower went via the 68 series and is now on 72.0.1 [ which hasn't affected our issue ] whilst the laptop seemed to get stuck until this week at about 63 . Both are configured to accept updates as they arise . I haven't yet used the laptop since 72 became available but it was working normally this am . I have signed up for the bug bit I think !