Warranty Check
My Iphone xs max can't not check hardware warranty on Apple website. I bought and activated it by my self on December 2018. Is there something wrong with it?
iPhone XS Max
It seems okay.
Most Apple software and hardware products include unlimited complimentary support incidents within the first 90 days of product ownership.
And, as per your screenshot, it shows March 27, 2019 as expiration date.
For any further doubts, contact Apple Support: Contact - Official Apple Support
Regards
Giulio