Hi Robert.
I only have 2 accounts. A personal account and another account that I access with my 3 colleagues in the accounts department.
My original query was there were no add-ins available on my personal account which I required.
There were also no add-ins available on the 2nd account but i assumed this was because the mailbox was being opened by 3 people.
So the current situation is that I have access to add-ins now on both of the accounts, but only because I am logging in via different browsers. I have tested this extensively.
But as soon as I open the 2nd account in the same browser, then both accounts seem to lose access to the add-ins.
To resolve this, I have to log out, close the browsers and login again.
So now I open one email account on Chrome and another on Firefox and this is working for me.
I have discussed with my Admin and he declines to do any further tests as the issue does not affect any other user who all have access to add-ins from their personal email.
So I thank you for your help on this.
Kind Regards