iphone 7 has been turned off for two weeks and now wont turn on or connect to itunes

i upgraded to an iphone x a month ago, but for the first two weeks i still used the iphone 7 for facetime etc, but then turned it off and put it in a draw, i got it out to use again as i need to send this iphone x back and it wont turn on at all and ive tried a hard restart and nothing and it wont connect to my computer at i think it need updating, but as it wont connect to itunes this cant be done, any suggestions