Can you post a screenshot of the Add-ons Manager window with the entry for Lightning visible? https://support.mozilla.org/kb/how-do-i-create-screenshot-my-problem

Thank you. I have posted the requested screen shot.

I see it was updated today. If that was done prior to opening TB this could be the cause of the problem? And if so how best to tackle it?

how about restarting Thunderbird?

Yes, I have tried that several times. I have posted a screenshot of today's error console showing error 0x80004005 when trying to open lightnting.

A google search showed the same error was solved by uninstalling lightning, renaming "storage.sdb" then reinstalling. However, that was 8 years ago and failed to work when tried 3 years ago. As I am not familiar with the functions of the various components of the profile I am loathe to fiddle blindly with the system.

If I am the only one reporting this problem it would seem the problem lies in my system and not in the upgrade to Lightning. Might upgrading to TB 45.4 be worth trying?

Losing my email data would be a problem but losing the calendar data would be an irritant I could recover manually. If uninstalling and reinstalling lightning is the simplest solution I could take that route. In that case what should I save/rename with a view to copying to the then newly produced profile or would it be safer simply to accept the loss and rebuild the calendar?

getthunderbird.com.

I suggest you try a full reinstall. It does not affect data or settings, but it might clear whatever program conflict is causing this issue.

Forgive my naivete but do you mean a reinstall over the existing programs or uninstal then reinstall?

Bramley said

Forgive my naivete but do you mean a reinstall over the existing programs or uninstal then reinstall?

Either

My problem remains. For info, in case it helps for the future:

1) I made a new entry in my calendar, closed and opened TB and found the new entry there but the rest still missing, 2) I reinstalled over the existing programs, 3) I uninstalled, deleted program folder and reinstalled, 4) I imported the latest known good .ics into Outlook, confirmed the diary entries were present in Outlook and exported a .csv file but TB/Lightning would not import it.

Thanks for your help but having spent this much time have decided to cut my losses and rebuild the calendar.

What about exporting as ICS?

Microsoft Office products have on the whole yet to make the leap to unicode. Microsoft made unicode the defacto standard for text in Windows back with XP, but they still use ANSI for almost all their applications. Excel in particular barfs on unicode text and insists on importing it, like it was a lotus 123 spreadsheet.

CSV as it is a text format suffers particularly badly from the mismatch of unicode and ANSI. In recent times I have fielded a lot of question about CSV and address books that come down to this unicode/ANSI issue. PErhaps it is the root cause of your import trouble as well.

Open the CSV in notepad, use save as and explicitly set the encoding as unicode from the default ANSI. That may be all that prevents the import.

Thank you but, after a concentrated effort, I have virtually completed the rebuild so will continue down this track.

However, I have noted your suggestion and the extra info. to retain for future reference.

I have decided to post a final update on this issue. Having rebuilt my data by hand everything worked well - until this morning. When I started Thunderbird all calendar and events data was missing.

I reverted to an earlier profile known to be good but to no effect.

I re-installed both Thunderbird and Lightning, again to no benefit.

It is barely 2 months since the previous incident. There is no identified reason for the failure, therefore I have totally lost any faith that the fault will not recur should I once again rebuild the data. Consequently I cannot contemplate continuing use of lightning.

When I started Thunderbird all calendar and events data was missing.

Did Thunderbird update prior to your loss of calendar data?

As before, what is the status of the Lightning extension? Please post a screenshot - see https://support.mozilla.org/en-US/questions/1142602#answer-925672

Your previously posted screenshot was of no use, since it doesn't show the status of the extension (Enable/Disable).

When I started Thunderbird all calendar and events data was missing.

With the previous experience you hopefully created a backup of your Thunderbird profile while the calendar was still working.

Thank you for your reply. To answer your points:

I have an automated daily backup and on both incidents I reverted to a profile which I knew had been good but no calendar data was shown.

I manage my own updates and the last was on 2nd December, since when I have used and updated the calendar daily.

On both incidents Lighning was enabled when I switched off and therefore was enabled when I switched on again only to find an absence of data. Indeed, if its status had been changed during close down or start up then there would be an even more serious problem.

However, as I said in my posting it was not intended as a question, just a situation update. Losing and having to rebuild data is not a trivial matter. For my data to be lost once is acceptable if it were recoverable, or at least had an understandable cause.

For the same thing to happen twice in 2 months is wholly unacceptable. I cannot have any faith that it will not happen a third time and am simply not prepared to put up with the risk. I will therefore not be using Lightning again.