fix google contacts sync issue on android

Hi I have a client who's phone has stopped syncing with google contacts in his gmail account all is fine but on his phone its stale for quite a while now in accounts all data shows as synced except for contacts which shows the 2 arrows for a month or so, as if it never finished I've tried most tip on the web, (clear cache, stop and restart sync) but so far no go if it makes a difference, his contacts are actually synced into gmail contacts from an external program. but that part is 100% okay here's the catch: my client is very security-minded, and cannot allow anyone to access his phone or account directly, so any instruction you may have will need to be sent to me, and i will be following your guidance thanks