Emails have been deleted since upgrade from Hotmail to Outlook

Hi,

I accessed my Hotmail account yesterday and was presented with a prompt stating that I had been upgraded to the new Outlook. This would have been fine however all of my emails and subfolders are now missing. This is a major problem as I had some very important emails residing in my Inbox and other subfolders. I would appreciate any assistance that could be provided on this matter.

When I access my emails on my phone the emails and subfolders still appear. I am no longer receiving emails to my phone therefore I assume it is no longer synchronising correctly. I am very concerned that these emails will now be permanently deleted and cannot express how important it is to get them back.

My email address has remained the same and has not been changed to the new Outlook address. I still am receiving emails through my account fine.

Note I have not deleted these emails by way of user error and I have tried restoring from my deleted items which has not resolved the issue (as specified on other threads as a solution).

Can someone please provide assistance for this?