May I ask are you using an official Samsung charger @NSB ?
Sometimes 3rd party chargers can take longer to charge up a phone.
Charging via a computer can take longer as can wireless charging.
I've read the phone does not support fast charging, and can take up to 3 hours to fully charge.
The phone was released in May 2018 so may also be behind in charging technologies.
Perhaps make sure the charging port is free of debris and try another official Samsung charger.
I wish you all the best. Take care. 😎
Daily Driver > Samsung Galaxy s²² Ultra 256Gb in Phantom Black.
The advice I offer is my own and does not represent Samsung’s position.
I'm here to help.