Iphone xs max update ios 15.1

What iOS are you running now?

How much available storage space do you have?

Are you on a “solid” WiFi connection to the internet?

What errors or messages do you receive when you try?

(it cerainly SHOULD update)

Thanks.

Note the message which reads, “This update requires at least 50% battery or to be connected to a power source.”

Based only on your screenshot, your phone appears to be NEITHER.