People have assumed I'm male online, even though my profile says "Mare" and has very girly colors If people still get confused, I'd be surprised since I have "female" or "she/her/hers" on my profiles.
I have only been mistaken as male IRL if people only have my name to go by, since I have a male name. I guess that's understandable. There's also been the case of people being too afraid to guess so they just use "they/them", which I honestly prefer over "he/him"!
It took me an embarrassingly long time to remember you're male! So sorry!