View Signal-pdf'S - muPDF-fail to mount

I have installed mudPDF in order to view pdfs in Signal Adroid app. Wenn I tap onto th epdf in Signal, muPDF treis to open but brings the error message “fail to mount” -“no document to open”

I can open the pdf if I save th efile and open it with documents.

Any other idea?

Have you tried the librera pro app. Opening pdf works good with it.