Max, 17, was last seen on Friday, October 15, according to police.
A spokesperson from Sussex Police said Max is known to travel across Sussex using the rail network.
The spokesperson added, “Max is described as slim, 5’9” with shaved hair on the sides and canerows (braided hair) on top, and brown eyes.
“He was last known to be wearing a navy blue tracksuit and carrying a black pouch bag.”
Anyone who sees Max or knows his whereabouts is asked to report it to police online or by calling 101 quoting serial 305 of 16/10.