Hi @Meike ,
I just checked details of your case and account and didn't find anything obvious amiss:
- Your Web Account is verified and has the required attributes for active support with PTC
- The SCN with which you opened the case is active
- The case is about a supported product (latest version)
At PTC we have a troubleshooting tool to "View as Customer" and we see the buttons there too:

Are you seeing the same problem on various browsers ? And did you try to empty your browser cache, clear down cookies for the ptc.com domain and restart ?
If you're still seeing the problem, please share some more details on browser version, exact symptoms, and also any errors you're seeing under the Console in your browser's Developer Tools.
I've added a comment for the engineer handing this case to make him aware of this thread, and to request that he makes contact with you directly in the meantime.
Thank you,
Peter.