Tubeless flats?

Hello, I got a flat tire while riding today. I bought the bike used three months ago, and the seller said the wheels were tubeless. I haven't refilled the tire since.

Air is coming out of my tire at the red spot without a visible hole.
I'm still really new to tubeless tires and I've read that you should regularly top up your tires. Will topping up the tire fix the flat? Or do I have to remove the entire tire and reinstall it tubeless? I'm new to this topic, so I would really appreciate some help.
Best regards AR