I have attached the "Pegasus" document to this solution as well.

If the XRL/Infor Add-In is not appearing in Microsoft Excel and you are frustrated that the  Add-In will not get into Excel, please find a possible solution in the attached document. 

Items to try:

 - update 1/10/19 - after a fresh install of office 365 1902 was giving issues at new customer site on two workstations.

- Firstly I installed 2010 microsoft tools pack.

- Then did an office repair online and changed the load behaviour to 3.

This worked for both workstations.

Lauren's entry 

Uninstalled XRL 
- went through document on knowledge base
- version is correct
- permissions are correct
- reg key changed, added to trust centre
- add in not loading in XRL

Installed .net 2.0 and 3.0 
- uninstalled XRL again 
- checked all settings - user has full rights to folder, local admin on machine
- add in still not appearing in Excel 
- changed all settings listed in knowledge base article

Other items to try:

-Full uninstall and reinstall complete inc manual reg deletion
-Not even adding addin manually on excel - error as above
-When changing load behaviour of reg addin from 2 to 3, when running the excel manual add it defaults back to 2.
-Not working as domain admin account
-Cant re register the dll file via cmd or run

-Windows firewall off
-AV turned off
-Re applied windows .net 2.0 and 3.0 features
-Full online repair off office suite through control panel. Ensure edition is semi annual, version no more than 1902 and updates turned off (This fixed the issue this time)