Bulb fit into socket.

Given the 9004 bulb is the only one specified suggest taking the old and new bulb to an auto parts store and letting the counter person look at it. They can pull bulbs off the rack and determine if there is problem.

 

I added pictures of a new 9004 lamp base. Hopefully you can see the shoulders in the bottom that keep the connector from going all the way in. I don't get it. Local auto parts place was no help.

 

See the difference however others have used this brand of bulb with success.

Check inside the locking ring to determine if there is a removable gasket (or something else) that is causing the ring to stick out further. If so, remove it.

PS:
With above compare the o'ring, gasket, etc on new and old bulb, locking ring and electrical plug and determine if something is different.

 

Except for the above mentioned, they are the same. However, I solved the.problem by taking a utility knife and cutting out the corners of the connector. See added photos.

 

Was thinking the same route but as a last resort.

Whatever works is fine.

 

It really wasn't that invasive. Just some thin plastic on the outside.