Just resurrecting this thread as I’ve been experiencing the same issue in recent days. I put a forum wide Notice out which appears until dismissed when viewed in some browsers but does not appear at all in others.
So far I know from user feedback those using Safari & Chrome can see it, those using Firefox and Opera don’t see it - and no it’s not been dismissed by the user inadvertently it just never ever appeared.
I've got a notice for visitors also, which is always present. I tested it with Firefox, Chrome and Edge and they all can see it without problems.
Not tested on Opera and Safari.