Check your settings are correct for the button
If that isn't the issue, book in for repair. It "may" be covered under warranty depending on when you bought your device and where from.
If you bought from Samsung, contact them directly (1 year warranty from memory).
If you bought from a network or retailer, contact them, they may even simply replace the device.
I am not employed by Samsung nor do I receive any remuneration as a Samsung Members Star.
My device is an S25 Ultra.