Text marker doesn't work under Acrobat for iOS

Hello!
I've been having a problem with the highlighter function for some time now. It doesn't work anymore. And just not with the Arobat Reader version for iOS.
I can rule out that it is the file because I can edit the file on the PC as usual.
When I select the text marker function and want to mark text, only a small rectangle appears that works like a magnifying glass.