Preview not working

Hi,

i use NC 18.04. After upgrade from NC 17 to NC18.1 my previews are not working.
If i click in the Share button, the Windows in the right corner are clear. With NC17 i have the previews of the PDF Files.

When i look with web tools, i see the following:

1. Request URL:

https://xxxxxxxxxxxxx/core/preview?fileId=29383&x=1680&y=1050&a=true

2. Request Method:

GET

3. Status Code:

404

4. Remote Address:

xxx.xxx.xxx.xxx:443

5. Referrer Policy:

no-referrer

I have already start the preview generatot with occ preview:pre-generate

But always the same.

Can anybody help?

Regards
Hermann