wifi sync not staying switched on

Hi,

Sorry if this has already been posted but I cant find it.

I have a iPhone 5s and I can not get the WI-FI sync to stay switched on.

I have connected the cable to enable WI-FI sync in iTunes and it all looks good on the phone and iTunes, as soon as I disconnect the cable the phone display says connect to computer using cable to enable WI-FI sync, but iTunes still thinks its enabled.

I've tried synching with it WI-FI sync off then on rebooted phone router computer in all different orders but I still cannot get it to WI-FI sync.

I have even downloaded remote and that works every time I open it so it has to be a silly setting somewhere and not my network connection.

Please can someone point me in the right direction

Kind Regards Mark

iPhone 5s IOS 8.3

iTunes for Windows 12.1.2.27