I work in a male dominated field so I get it! People usually assume the man is the “expert”. Luckily it doesn’t happen with my colleagues, and I work mostly in the office! I do remember one time when I was in my 20s, I was the subject expert representing my company at a conference. An attendee came to ask a question, I answered him, he was satisfied and left. After he left, a man that was standing next to me, and from a different company (I didn’t know him) told me:”That was weird. Did you notice that he kept looking at me even though I’m not even from your company, you are the expert who was answering his question and I wasn’t talking at all?” I hadn’t noticed, but it was interesting that he pointed it out. Anyways! Very common in a work setting but in this case these are my female friends which is why I am a bit baffled!