Changed O2 sensor, now car will not start

My 1996 Honda Odyssey is working perfectly except for a check engine light (which Pep Boys diagnosed it for free and told me upstream oxygen sensor).

So, I purchased a brand new (non refurb.) Upstream oxygen sensor and install it (I forgot to disconnect the negative battery). I go to start the car and the car will not start (meaning it won't even crank)! There is plenty of battery juice and all the lights come on in the dash (except for the usual check engine light), but the car will NOT turn over and even attempt to start. I tried to give it a jump, but to no avail. The battery is perfectly fine. Only 1 month old! I checked "ALL" fuses under the hood and in the car and they check out perfectly. I even replaced some of the fuses with new ones, just to make sure. When I turn the key, the car doesn't even start at all or attempt to start. My first guess is something electrical. Ever time I turn the key, I hear the fuel pump trying to work, but the car will not start. Do I have to reset the ECU in order for the car to start? I currently have the negative and positive battery connections disconnected and I am waiting awhile for that route.

I have also reinstalled the previous oxygen sensor that was on the car, but that did NOT work either. Lastly, in the past few months, I replaced fuel filter, spark plugs, distributor cap & rotor, spark plug wires, air filter, oil filter, PVC valve, and two new oxygen sensors! There is half a tank of gas and plenty of oil and all other fluids.