I removed the old oxygen sensor and tried to put in the new one, but it won't on 1991 GMC 1500 Pickup

fit????Why and what do I do now since it won't pass inspection because h20 is too high??

Asked by for the 1991 GMC 1500 Pickup
Threads damaged.Get appropriate size tap and re-thread.
2 more answers
wrong part
Someone sold you the wrong sensor...Ask for a upstream if the sensor is on the manifold...