We have created Outlook Ribbon Webaddin. It is working as expected(ribbon Addin) and loading in top ribbon place. But for some customer, it is loading as contextual Addin.
Manifest URL : https://www.backflipt.com/app/addin/Backflipt-Beta.xml
Outlook diagnostics info :
{"host" : "Outlook", "platform": "PC", "version": "15.0.0000.0000"}
Is there any way outlook configuration affects manifest loading way?
Check the below image(blurred for security reasons) :
Green color section is the plugin which is loaded as contextual addin

Seems it is not an issue with outlook mail box version or client version. I can see Cisco webex is installed in his ribbon. If it is because of version, then he should not able to install any in ribbon right.