Dynamic PDF - invisible signature

Hello everyone,

I have a problem with a PDF file that was just sent to me. The sender assures me that it has been digitally signed, but when I open it, the frame for the signature has disappeared and the signature itself is not visible.

I tried opening it with the latest version of Adobe, as well as with PDFArchitect and directly on Edge.

I tried opening it on my smartphone and with the Android viewer, I can see the signatures, but when I attempt to print, they do not appear on the printed file.

What solution do you have to fix this issue, please?

Thank you in advance for your help.