The issue was recently address changes, which was showing vacant but now its resolved i started receiving mails there is no problem with it. My question was whether to worry about the notice from USCIS that i request for the redelivery. i received the response letter to my inquiry but the actual notice to my application still hasn't redelivered. the response letter says that they have submitted but instructed me to wait at least 15 days to be redelivered.Based on what you previously described, the issue is USPS related. You need to sort that out with them.