RED rectangle instead of barcode on Android Adobe Acrobat

[Tom Comb]

When I open some PDF on my Android (OnePlus 7, Oxygen OS 10.0.1) using the Adobe Acrobat app I see a red rectangle instead of the barcode.

I read similar problems on the forum, but always you ask for desired file instead of explain where is the problem, and how WE, THE COMMUNITY, can solve it. 

WHY?

-

With regards

Tom

[Tom Comb]

Anyone can answer? Or maybe how solve this problem?