Simply disable Avaya add-in if you cannot see outlook reminders popups

MS Outlook 2016 was not showing my reminders popups since a few weeks, first I checked reminder settings in outlook:

File --> Options --> Advanced --> Reminders

it was already activated, then I have tried other solutions like deleting the relevant registery key, and clearing reminders, but no luck!

Finally I found that disabling Avaya will solve the problem, here is the steps:

Goto: File --> Options --> Add Ins

Make sure "COM Add-ins" is seleted then click "Go"

Uncheck "Avaya Collaboration Services"

Click OK then restart outlook, all missed reminders will popup in outlook window.