Can you post your Troubleshooting Information? Help (Alt-H) - Troubleshooting Information

Sorry - not sure what is meant by that

Just a check, You did install it from file in Thunderbird and not in Firefox. That has happened before. in Tbird open help (or press Alt +H) and select Troubleshooting information Use button Copy to clipboard and paste it in here.

Thank you

Pasted from Tbird help

 Application Basics

   Name: Thunderbird
   Version: 38.1.0
   User Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0
   Profile Folder: Show Folder

             (Local drive)
   Application Build ID: 20150707103124
   Enabled Plugins: about:plugins
   Build Configuration: about:buildconfig
   Memory Use: about:memory

 Mail and News Accounts
   account1:
     INCOMING: account1, , (imap) mail.btinternet.com:993, SSL, passwordCleartext
     OUTGOING: mail.btinternet.com:465, SSL, passwordCleartext, true

   account2:
     INCOMING: account2, , (none) Local Folders, plain, passwordCleartext

 Crash Reports

 Extensions
   Lightning, 4.0.1.2, true, {e2fda1a4-762b-4020-b5ad-a41df1933103}

 Important Modified Preferences

   Name: Value

     browser.cache.disk.capacity: 358400
     browser.cache.disk.smart_size_cached_value: 358400
     browser.cache.disk.smart_size.first_run: false
     browser.cache.disk.smart_size.use_old_max: false
     extensions.lastAppVersion: 38.1.0
     font.name.monospace.el: Consolas
     font.name.monospace.x-cyrillic: Consolas
     font.name.monospace.x-unicode: Consolas
     font.name.monospace.x-western: Consolas
     font.name.sans-serif.el: Calibri
     font.name.sans-serif.x-cyrillic: Calibri
     font.name.sans-serif.x-unicode: Calibri
     font.name.sans-serif.x-western: Arial Unicode MS
     font.name.serif.el: Cambria
     font.name.serif.x-cyrillic: Cambria
     font.name.serif.x-unicode: Cambria
     font.name.serif.x-western: Cambria
     font.size.fixed.el: 14
     font.size.fixed.x-cyrillic: 14
     font.size.fixed.x-unicode: 14
     font.size.fixed.x-western: 14
     font.size.variable.el: 17
     font.size.variable.x-cyrillic: 17
     font.size.variable.x-unicode: 17
     font.size.variable.x-western: 17
     gfx.direct3d.last_used_feature_level_idx: 0
     mail.openMessageBehavior.version: 1
     mail.winsearch.firstRunDone: true
     mailnews.database.global.datastore.id: b69b4ad4-7667-4583-8d4a-69dec40447b
     network.cookie.prefsMigrated: true
     network.predictor.cleaned-up: true
     places.database.lastMaintenance: 1439204369
     places.history.expiration.transient_current_max_pages: 104858
     plugin.importedState: true
     plugin.state.npctrl: 2
     plugin.state.npitunes: 2
     plugin.state.npmcsnffpl: 2
     plugin.state.npspwrap: 2
     privacy.donottrackheader.enabled: true
     security.disable_button.openCertManager: false
     security.disable_button.openDeviceManager: false

 Graphics

     Adapter Description: AMD Radeon HD 7660D
     Vendor ID: 0x1002
     Device ID: 0x9901
     Adapter RAM: 512
     Adapter Drivers: aticfx64 aticfx64 aticfx64 amdxc64 aticfx32 aticfx32 aticfx32 amdxc32 atiumd64 atidxx64 atidxx64 atiumdag atidxx32 atidxx32 atiumdva atiumd6a atitmm64
     Driver Version: 15.200.1046.2
     Driver Date: 7-15-2015
     Direct2D Enabled: true
     DirectWrite Enabled: true (10.0.10240.16390)
     ClearType Parameters: Gamma: 2200 Pixel Structure: B ClearType Level: 100 Enhanced Contrast: 50
     WebGL Renderer: false
     GPU Accelerated Windows: 1/1 Direct3D 11

     AzureCanvasBackend: direct2d 1.1
     AzureSkiaAccelerated: 0
     AzureFallbackCanvasBackend: cairo
     AzureContentBackend: direct2d 1.1

 JavaScript

 Incremental GC: 1

 Accessibility

   Activated: 0
   Prevent Accessibility: 0

 Library Versions

     Expected minimum version
     Version in use

     NSPR
     4.10.8
     4.10.8

     NSS
     3.19.2 Basic ECC
     3.19.2 Basic ECC

     NSS Util
     3.19.2
     3.19.2

     NSS SSL
     3.19.2 Basic ECC
     3.19.2 Basic ECC

     NSS S/MIME
     3.19.2 Basic ECC
     3.19.2 Basic ECC

You chose a solution, does that mean you solved the problem? Otherwise open it again.

Sorry - didnt realise that was a solution.

Actually I have got to the point where I have almost lost the will to live and will go back to Outlook where there was at least something I found easier to understand.

Sorry to hear. When you install 38.1.0 you get a opportunity to load Lightning as it is now bundled wit Tbird. You don't have to download and install it.

So if it doesn't work I would suggest a reinstall of Tbird. (Download) Make a backup of your profile first, just for safety. Manual backup

Thanks for trying Gnospen but reinstalling doesn't work either. Lightning is shown as an extension with options to disable or remove so I asumed that it was enabled but there is no sign of it anywhere

You dont have the option on the bottom of your Tbird screen to install? The add-on Lightning should also have "options" as an alternative.

Try disable and then enable. The option on bottom of your ordinary Tbird screen might show up. If not, delete Lightning and reinstall it as a regular add-on. (Download) Or if you prefer reinstall Tbird. With lightning deleted it shouldn't skip the option to install Lightning.

Thanks again Gnospen. I think, amongst everything that I have tried including disabling McAfee, that I have already done that but I will try it again.

Nope - still in square one. Lightning again shown as installed on the extensions list with options, disable and remove shown. No other sign of Lightning anywhere either on TB or FF.

Think I read this in another question. If your screen has a low resolution and you have Tbird at full window. maybe just changing to a smaller window will give you a chance to scroll down.

And option doesn't open standard option?

It opens the same options as options on the tools menu for TB

With or without the calendar menu-option?

Of the three you have ringed only the two on the right - nothing on the left that might indicate Lightning

And what happens if you click on one in the upper corner? or press F11 or Ctrl+shift+C or Ctrl+shift+D

I think I may have been wasting your time for which I apologise. I think lighning has been there all the time and I was expecting it to be shown on the menu bar as lightning which may have been the case in earlier versions perhaps. Thank you for your patience.

Thats fine, glad you found the light :)