This problem has been popping up for our users the last year: Whenever a user would start Outlook (after reboot or simply restarting Outlook) the Skype Meeting Add-in would be missing from the ribbon and had to be manually enabled to show up again.
In my experience the problem is not consistent between users with the same OS version or even local administrator privileges, but the solution was nevertheless easy in the end.
After trying all the official tips of
- Simply enabling the add-in (works for the current session, not after Outlook restart)
- Repair the Office installation
- Verifying the registry key of the add-in “LoadBehaviour” (should be the value “3”)
Situation still persisted, the user would have to manually enable the Add-in via the menu File -> Options -> Add-Ins -> COM Add-ins. Not a permanent solution.
What works in the end, and is covered in other blog posts, is this:
- Run Outlook as administrator (no need to set up a new account/mailbox if your logged-in user is not local admin)
- Navigate to File -> Options -> Add-Ins -> COM Add-ins. Now simply remove the Skype Meeting Add-in from the list.
- Re-add the Meeting Add-in from the same menu. Path to the add-in is dependant on your Office version. The add-in itself is named UcAddin.dll
- If you are running x86 version then the path is %programfiles(x86)%\Microsoft Office\Office 16 for Outlook 2016 or
[..]\Office 15 for Outlook 2013 - If your are running x64 version the path is
%programfiles%\Microsoft Office\Office 16 for Outlook 2016 or
[..]\Office 15 for Outlook 2013 - This may differ if you are running Click-to-run Office version
- If you are running x86 version then the path is %programfiles(x86)%\Microsoft Office\Office 16 for Outlook 2016 or
- Now close Outlook and restart in your regular user context.
Add-in should be available again.
Rune's blog about things I see and UC 
https://www.unh.edu/it/kb/article/skype-for-business-new-skype-meeting-button-missing-from-outlook.html
That link only refers to my first bullet point of things I tried and which did not work – isolated.
Without ensuring that you are running Outlook with administrative privileges (which is a best practice if you have an enterprise environment) that will simply not work, the plug-in will still be missing the next time Outlook is restarted.
Rune,
Instead of Manage COM Add-on, need to select Manage Disabled Add-Ons, from the drop-down. Please have a look at Mike Zawa’s response here:
https://answers.microsoft.com/en-us/msoffice/forum/msoffice_outlook-mso_windows8-mso_2013_release/skype-meeting-add-in-for-office-2013-wont-stay/f079c405-a610-43eb-b9bf-627061d9c9d5?auth=1
Have you seen this add-in cause skype meetings to crash?
Sorry, I meant to reply to Saby, not Rune…
Please check Mike Zawa’s response here
https://answers.microsoft.com/en-us/msoffice/forum/msoffice_outlook-mso_windows8-mso_2013_release/skype-meeting-add-in-for-office-2013-wont-stay/f079c405-a610-43eb-b9bf-627061d9c9d5?auth=1
Thanks a lot;
i’ve been searching for a definitive fix and finally…
Hi, I believe that there is a step that is missing from many self-solve instructions:
The Add-In can become “Disabled” – and the solution is to REMOVE it from the DISABLED list. (not remove it from Outlook)
Look at the solution from Mike Zawa on this forum:
https://answers.microsoft.com/en-us/msoffice/forum/msoffice_outlook-mso_windows8-mso_2013_release/skype-meeting-add-in-for-office-2013-wont-stay/f079c405-a610-43eb-b9bf-627061d9c9d5?auth=1
Here is a video that shows the process: https://youtu.be/9Z5ZqwtK9ZI
WOW!! this worked liked a charm.
Thanks Rune for the posting. I followed your instructions and I think the issue has been fixed now. Thank you so much! Just wanted to point out that now it is called “Lync Meeting Scheduling Outlook Addin” instead of “Skype Meeting Add-in for Microsoft Office 2016”.
I tried this but the file was saved in C:/Program Files/MicrosoftOffice/root/Office16
The first time I tried it, it didn’t work. When opening as an admin it will ask me to set up an email account which is not necessary. I deleted the add-on and re-added it from the location above (it will change the name of the add-on to Lync) – it would save as “Load at startup”. I then re-opened Outlook and it would be disabled again and funnily enough although it was there (with the different name – so it was added correctly) it was now saved as “Unloaded”. Bear in mind that these files are correctly set up in the registry with the value 3 so they should load at startup. I opened Outlook again in admin mode and removed and re-added the file. But this time it worked for some reason and Outlook now started with the Skype Addon every time.