MarkInfo and StructTreeRoot missing when generating PDF/A 1-a file in Latex

Question

I need to submit my thesis as a PDF/A 1-a file but I am having issues in generating the file from Latex. I have several problems (one with Transparencies) but I think the main issues go down to missing MarkInfo and StructTreeRoot. I have to admit that I am completely ignorant and I have no idea what they are.

I am using TexStudio and I tried compiling the file both with Latex and PDFLatex. I am following the pfx package guide but I am getting the same problems when checking the file with two different sources.

With 3 heights PDF validator I get:

• "The key MarkInfo is required but missing." and

• "The key StructTreeRoot is required but missing."

With Vera PDF checker I fail the following tests:

• "The document catalog dictionary shall include a MarkInfo dictionary with a Marked entry in it, whose value shall be true." and

• "The logical structure of the conforming file shall be described by a structure hierarchy rooted in the StructTreeRoot entry of the document catalog dictionary, as described in PDF Reference 9.6".

I reduced my code to a simple example:

\begin{filecontents*}{TEST_Meta.xmpdata}
    \Title{This is the title}
    \Author{Author ABC}
    \Language{en-US}
    \Keywords{Test \sep 123}
\end{filecontents*}
\documentclass[11pt,a4paper]{article}

\usepackage[utf8]{inputenc}
\usepackage{colorprofiles}
\usepackage[a-1a,mathxmp]{pdfx}
\usepackage[T1]{fontenc}
\hypersetup{pdfstartview=, bookmarks=true}
\usepackage{lmodern}

\begin{document}

I am just a test.

\end{document}

From what I understand, I miss to specify something in the metadata but, as I said, I have no idea what is missing since I am totally not familiar with this and after some googling I didn't find anything.

Do you have any clue?

Thank you very much!