check both bulbs and the fuse. If the bulbs and fuses check OK, perhaps a bad ground around the bulb socket, compounded when you fiddled around replacing the bulbs.
I don’t know if you have one of those multi purpose bulbs, a circuit for flashing and a circuit for braking (2 filaments). You could also switch bulbs from right to left. At least you will find out if it is bulb related or wiring related.
Double check that you have the correct bulb, be sure that it’s properly oriented (many have one little orientation bump higher than the other), and be sure that it’s fully seated. Almost always these types of symptoms are caused by an incorrect bulb, a bulb not properly installed, or a bulb not properly seated.
If they are dual filament bulbs, it might be the alarm filaments are ok, but the brake light filaments are bad. It’s not uncommon when changing out a bulb to discover another bulb in the same fixture then won’t light. That happens b/c the filament gradually burns away to a tiny thread over time, and when you change one bulb it disturbs the other bulb’s filament enough to break it. I had that happen to me the other day in fact, changing out one bulb caused the other bulb in the same fixture to fail.