Mailboxes not showing in old version outlook 365 on mac

So i have a lot of email messages in outlook that i need. I moved to another hosting provider and restoring a backup is not an option. The emails als older then 5 years.

Using the older version of outlook should be the soluition, but i dont see any mailboxes in the older version. When i search for some attachments from the emails, i can find them in different submaps from:
/Users/macbook/Library/Group Containers/UBF8T346G9.Office/Outlook/Outlook 15 Profiles/Main Profile/Files/S0

So i know the emails are still there. When i switch to the new version of outlook i can see all my mailboxes, but the one with the old settings from the old previous hosting provider doesn't have any messages.

How can i fix this problem?

I really need those email messages, so i can export them and import them to the new hosting provider.

Kind regards
Ivan