Just go to dmv and ask for an extension. I had the same issue last year and all they did was tack on a few dollars to my reg. Only liike $3 if i remember correctly. Not bad though considering the fine for driving without reg if you were to get caught. Or you can file for a non op if you have a secondary vehicle you can drive until the part gets here.
I didn't have any issue getting an extension, but I did need to go in person to request it. I was given. another couple weeks. Maybe they might want to see the failed test? But I didn't have anything, and they gave me a little extra time. They don't seem to penalize you for going over the date, as long as you don't drive the car till it passes the test.
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