When a document name is entered for an accessible PDF in InDesign under File > File Info, it is automatically included in the PDF.
When checking accessibility in Acrobat, an error message is generated if a document name is missing.
If you change the title in File > Document Properties and save the document, the problem will be resolved. This also applies if you subsequently restore the original title.
It appears that the title from InDesign is not properly embedded in the PDF or is not correctly recognized by Acrobat.