The whole time I was able to download the received pdf files on the laptop via Chrome via t-online Mail Center. Recently, however, this no longer works and an error message always appears.
What can I do?
Recently (…) an error message has always appeared.
It would be helpful if you could show / tell us the exact wording of the error message (possibly with a screenshot) …
Somehow that the file would be faulty. Resending does not bring anything and restart etc I have already tried
You have already been told about the photo / screenshot of the error message.
In many cases this can be an excellent way of solving problems.
But if you have problems with Chrome, try the Firefox browser.
It has nothing to do with Chrome (even under the hood).
Maybe it will work with that.
Otherwise, contact T-Online support.