Check the PC connection, the setting, cable seating, port lint, temperature and charge level first. If it is still slow, look for PPS in the charger specs: a high-watt charger without PPS may not super-fast-charge.
The wattage printed on a charger is a ceiling. USB PD fixes a maximum for each voltage step, going past 100W requires a separately certified 240W cable, and a 65W three-port charger drops its main port to 35W once every socket is in use.
Even with the same "fast charging" label, actual speed depends on USB PD support, PPS notation, and wattage. This post covers reading PD voltage profiles, why Galaxy ultra-fast charging requires PPS, multi-port output distribution, and 5A cables — based on published specifications.