Hi Marilee.
Thank you for your prompt reply.
After following your details I was getting no luck. Then by chance I decided to look at which tenant I was on by clicking on the user icon (top right) while in https://myapps.microsoft.com. I didn't realise the current tenant is located at the top left of this pop-up and was not the correct tenant. I clicked on "switch organisation" and found that this email address had been registered as a new guest on a number of tenants. So I selected the correct organisation in the drop down and hey presto. All good. This is something that would be very easy to miss so I am going to add the "tenant id" parameter to the link i.e. https://myapps.microsoft.com?tenantid=<tenant id>
Thanks.
John.