PDF Error: Invalid file without explanation - XML is valid, PDF is PDF/A-3B

[Jetro223]

I get a validation error.

But no explanation why the file is invalid.

The XML data itself validates.

And according to https://erechnungsvalidator.service-bw.de/ it's also valid

The PDF is in the format PDF/A-3B.

How can I get details about the validation error?

[jstaerk]

Which version are you using in which language on which platform with which file?
I can not replicate not having a "show more" link

https://www.portinvoice.com/ is a frontend for the mustang validation which you could try and for PDF validation Quba uses Mustang which embeds verapdf, i.e. if you suspect that the PDF/A is invalid you could download https://verapdf.org/ and have a look.