The relay seems fine and should work with OpenSprinkler. Could it be that you wired the relay incorrectly? Note that the correct way is to connect the two coil wires to OpenSprinkler just like a normal sprinkler station (i.e. one wires goes to COMMON, the other goes to a station port). The coil resistance should be around 30 to 40 ohm as the datasheet suggests.
It’s possible that the fuse on OSPi has burned. To check you can use a multimeter to measure the resistance across the fuse (it’s a small brownish component right above the green COM terminal block and it’s marked N). If the resistance is not close to 0 that means it has burned out.