It was on MeTV (a syndicated oldies station that is carried on over-the-air secondary digital channels by a lot of local TV stations) for a while, but isn’t carried by them these days.
It looks like your best options to watch it now are:
- FETV, a cable oldies station, which is on some cable systems, has it on their schedule
- Amazon has DVD sets of the first three seasons for $10-$15 each