O2 Sensor Test "Not Ready"

For my 96 Grand Cherokee 6-cyl, can anyone please tell me why I am getting "Not Ready" statuses on my non-continuous tests (O2 Sensor, O2 Sensor Heater and Catalyst)? I replaced the O2 sensor and the O2 was testing fine, then it went back to "not ready" again. Car runs fine, no trouble codes and I have driven plenty of miles for the tests to complete. Please help!

Did you get a bosh or ac delco o2 sencer? I know gm cars and jeeps only like ac delco parts.

After driving 200+ miles, all 3 non-continuous tests completed okay, then I turned off the engine, started it back up and all 3 test went back to "not complete". The new O2 sensor is a Bocsh, but it seems to be working fine. The battery is strong, no trouble codes...Does anyone know what the heck might be wrong?

I think its the Bosh that is doing it. Im Not putting down bosh or anything, but american cars do well with as delco parts, they have trubble reading bosh o2 sencers.