file upload fails with error

Hi all!
file upload fails with error “unexpected response status code 406”

Who then had such an error?

tried it in different ways. does not work

Check the log files. What browser? Your browser or a proxy could be stripping off the accept header in the request. That could cause the server to throw a 406.

Tried different browsers, no result
Loading goes fine if I load .xml in “Vendor Configuration File”
I didn’t find anything in the logs