I am sorry to hear about this, there are three main reasons that cause this. Either you ordered the wrong starter, you have a weak battery or possibly your cables have corroded and not enough power is coming from the battery to the unit.
First verify the part number of the old starter you took off so that we can verify you ordered the correct unit.
Next retest your battery. Even if you battery was recently tested, it is a battery after-all and if there is something wrong it can easily discharge in a couple of hours.
Finally, use a volt meter to check the power at the stud on the starter.
If all of these check out. Give us a call at 586-257-1515!