First, all our answer rely on your claim that your breaker is "just like this one". That one is a CAFCI. If your breaker is somewhat different, then all our advice is no good. The good news is Square D takes button color pretty seriously, and white-button Square D's should all be CAFCI.
Chasing an arc fault
Move through each of the switches, then receptacles, then lamps and check these things.
Ground wires touching screws. Make sure that as the devices are pushed back into the box, you don't have a ground wire getting near a hot or neutral screw.
Backstabs. Arc fault breakers were initially developed for electric blankets. But they discovered they were really good at detecting another wiring fault: Backstabs. Backstabs are when you have #14 wire and you just jab it into the provided hole on the recep or switch. . The mechanism is surprisingly hokey - after all you are getting 4 of these for 50 cents. They regularly cause circuit burnout, and AFCI breakers are proving they cause a lot of arcing before they burn out.
So I recommend working through the switches and receps on that circuit. For each backstab connection, firmly pull and twist the device back and forth while pulling the wire steadily out (no need to waste wire length unless you have loads of it). Then move the backstab wire to the nearest screw. If the screw is already occupied, someone is cleverly using that trick to do a splice, and you should pigtail those 2 wires together with a pigtail going to the switch. I do not recommend getting any fancier than that, or else you need to take a crash course in replacing receptacles - issues like tabs broken off, 3-way terminal colors, all that jazz. It's way more complicated than it ought to be.
Wire nuts. Bad wire-nut jobs are a common cause of arc faults. First, are the wire nuts taped? Exception: A wire nut on a single wire should be taped (otherwise the nut will fall off).
Tape on a wire-nut usually means the installer has learned that wire-nut connections will fall apart if not taped. That is because the installer's bad technique. The same thing that makes them fall apart also makes them arc. So, the moment you see tape on a wire-nut, take it off. Then, give the wire nut a "pull test". Grab the nut proper and pull hard on each wire one at a time. If the wire pulls out, that was a bodge job that needs to be re-done. Make sure the bared section is at least 80% of the length of the wire nut and no more than 95%. It will stick out initially, but get sucked in as you twist.
Wire length is precious - do not cut off the curly bits, just coarsely straighten them. Put the wires back together with ends even. Then put a new, good wire nut like an Ideal brand on it, and crank HARD, and clockwise - same as screws, bolts and nuts. DO NOT pre-twist - if you are tightening hard enough, the wire nut will do that for you, believe you me! If the wire nut is not twisting the wires, you're being way too much of a soft touch. This is one place where you want "gorilla tight, not monkey tight".
Now you do a pull test on it just like that, and it better pass with flying colors. If not, refine your technique.
If you're having trouble getting multiple wires to stay even as you set them up, feel free to tape the wires together, say into 2 groups, about 2" back of the wire end, before putting them into the nut. Then nut it, remove the tape and pull-test.
