dnd 5e crossbow help

hi im kind of new to the game and i need help, i dont know if i configured something wrong either in roll20 or on my browser but every time i open the game my crosbow bolts damage is switched to STR and as far as everyone has told me so far, crosbows use DEX so i dont know what im doing wrong, i have to change it every day to dex.
im playing a DEX fighter