It says iPhone warranty expired

The model number you provided is for an iPhone 6s. The only way this warranty could be expired is if this was an out of warranty replacement model for a device that was user damage. That would only carry a 90 day warranty. That is the only thing I can think of that would result in your device being out of warranty.

If you used the link that Michael provided you earlier to put in the serial number and it says there is no warranty, then my example could explain it. The app that you used is not always accurate for manufacturing dates, and besides, the date of manufacturer does not have an affect on the warranty date.

Where did you buy it? If it was not purchased from Apple or an Apple Authorized Reseller, then the warranty started whenever the first owner purchased it at retail. Warranty is from the date of original retail sale by Apple or their Authorized reseller.

This is the only legitimate site to check coverage - https://checkcoverage.apple.com

Neither Apple nor its Authorized resellers sell refurbished devices at retail. I'll ask again, where did you buy this phone? If you bought it used, it could just be a registration glitch, but no way to know. If you bought it new, you have a receipt presumably and that will establish the purchase data and thus the start of the warranty period.

Chris, that would not be correct. A service replacement iDevice has either the remainder of the original warranty or a 90 day warranty, whichever is longer. So there would be no way that phone could have no warranty other than a glitch, it is a demo phone, or was stolen prior to retail sale.

I'm not sure that a replacement phone for a device that was user damaged, such as water damage would have the balance of the original warranty. I may be wrong, since this is just a hypothesis on my part given the fact that water damage would void the warranty. A water damage replacement out of warranty should only have a 90 day warranty, and depending on when it was replaced versus when the used purchase was made, the 90 days could have expired.

Again, I could be wrong in my interpretation of the out of warranty replacement. Either way, I would suppose that if necessary, the OP could contact Apple support for any verification.

It should carry the balance of the original warranty. I don't see how a 6s would return the specific message the OP is getting when checking the warranty status at all to be honest... I would expect a stolen phone, or a demo phone would return the message that the device has been replaced. Service replacements should still be in warranty until the expiration of the original units warranty.

I suspect a glitch in the database. Best the OP contact Apple directly.

Thanks. I appreciate and respect your input. And KiltedTim, I agree the best bet for the OP is to contact Apple Support directly. I wouldn't be relying on an app to provide me with that type of information.

Are you positive it's a 6s and not a 6? The 6s hasn't even been out for a year yet. It's not possible for the warranty to be expired.

When you go to Settings>General>About>Model, what does it say?

Where EXACTLY did you buy it? Are you going by the serial number in Settings>General>About or the serial number on the box?

What is the model number in Settings>General>About?

That is one of the advantages of the out-of-warranty service rather than going to a 3rd party, it restores whatever warranty it has left.

I wonder... I someone took a physically damaged phone to the genius bar and refused out of warranty service, would they flag the warranty as expired in the database?

Just a thought.