Juan Vega Uriostegui was last seen in the Solefields Road area at around 10.20am on Sunday 10 October 2021.
The 16-year-old is described as being five feet and five inches tall, of slim build and with shoulder-length, wavy black hair which is sometimes worn in a ponytail.
A CCTV image of Juan soon after he was last seen, shows him wearing blue jeans and a blue hooded top with a white emblem on the front. He is also carrying a brown shoulder bag, a black rucksack and a plastic carrier bag.
Inspector Vicki Withnall said: ‘We know that Juan travelled to London on the day he went missing and it is thought he has also worn black clothing and a black face mask whilst there.
‘We are asking anybody who has seen him in the last ten days, or knows where he might be, to contact us immediately.’
Anybody with information is urged to contact Kent Police on 999 quoting reference number 10-1330.