If Amazfit is not syncing with Strava try this.
Every other day Amazfit fails to sync to Strava so here's a simple enough manual upload solution. Open Amazfit app > activities > top right corner (box with arrow) > Export track - gpx file gets uploaded to your internal storage in Amazfit folder. Next go to http://www.strava.com/upload/select > choose files > look for amazfit folder in phones storage > file is uploaded. Takes about a minute. Advantage of this method is that it gives you the opportunity to re-name your activity and add a comment instead of the automatic sync where you have to later re-edit it.