Yamaha mx49 sustain pedal stopped working, but pedal is working properly.

Huh? Please explain... by itself this is not clear... and totally contradicts itself.

It’s a riddle? Perhaps... is the answer: the musician forgot to press the pedal ???
(Sorry, couldn’t resist...) what really is happening? Suggestion.... test it on an acoustic piano sound

Troubleshooting
Is it an FC3A Type (TRS) or FC4A Type (TS) Yamaha Sustain Pedal?
Is the Foot Switch parameter set to the correct type of pedal?
___ Go [UTILITY] > select “Controllers” > then select “FS Pedal”. Determines which model of an optional Foot Switch connected to the [SUSTAIN] jack is recognized.
Is the pedal plugged into the correct jack and is the plug fully inserted?

Sustain pedals do not work on Drum Kit sounds.
Sustain pedals do not work on sounds with a “percussive envelope” - technically, when AEG Sustain Level = 0
Sustain pedals behave differently when applied to a Part under Arpeggio control, the pedal takes the place of you holding down the Keys — which in the case of an Arpeggio Part means the Arp Phrase continues to run until you let go.

Most Common Error:
Wrong jack (don’t laugh, number 1 error)
Best results happen when directly looking at the back panel straight on - versus reaching over the top.