Transmitter may be still running, just at lower power or it might be the same broadcast on a different transmitter. Do you hear any beeping in the audio from the online broadcast?
...or a new closer tx'r who's frequency is close enough that its' carrier overrides and blocks NOAA's in your area.
Reminds me of the time years ago I learned I could block dad's easy listening FM station by tuning my radio 10.8 Mhz lower.
Had to love those poorly-shielded IF cans!!!
I remember one of the regional FM stations was using its standby tube transmitter and it put out a spurious that wiped out another station (a company CO-OWNED station, BTW!!!) exactly 1 MHz down the dial...
And about 30 airline miles distant!!!!!
The engineers wouldn't believe me...then they listened on their own receiver at their studios ("Gee....we don't usually listen 'off-air'...."!!
)
Did I mention....the problem was fixed in under an hour....and at least one engineer was
!!!