After installing the Outlook Plugin, the tab is not shown and no errors are appearing when you try to enable to plugin.
If you go into options -> add-ins and manage com add-ins the box for CRM outlook plugin remains unticked and will not change.
No errors are shown even if debugging logs are enabled
Resolution / Fix:
Go to Outlook Options -> Add-Ins -> manage Disabled Items and click 'Go' as shown here:
You can click on the disabled outlook add-in and click enable. You will need to restart Outlook to see the changes.
If the tab is still hidden, select COM Add-ins and make sure the box is ticked.