outlook web calendar can't create teams link

Hi, 

in another post I asked how to reply-by-teams-meeting, and Teresa_Cyrus gave some great suggestions. However, the issue is that I can't create a Teams meeting through Outlook Web at all, the toggle switch in Outlook web is missing (compare my screenshot below to Teresa's in the other post).

Our institutions has full subscription to Office365, and I can happily create Teams meetings with Teams.

I have tried Outlook PWA, Firefox and Chrome, on Linux and Windows without success. I also had a colleage try, and he had no problem and the Teams toggle switch appeared as expected for him.

So it might be an issue with

1) my settings in Outlook somehow disabled the Teams toggle or

2) my account(s), as the eMail is associated with both a private Microsoft account and with the institutional tenant , or

3) something else. 

To elaborate on 2), when logging into office.com, I enter my eMail adress, and then a notice appears that my eMail is associated with two Microsoft accounts, namely a private Account I created back in the days myself, and a business/educational account created by my institution, which has the Office365 subscription. Any ideas what to try next ? 

Thanks in advance, 

yours,

Steffen