Here’s how I made a rival move from a position you don’t use radio put you place a marker then remove and the rival tends to move when you do that so you just repeat it but it some times does not work.
Rivals (actually all machines) move when you’re about 500m radius of them. If you are further away, game isn’t going to calculate machine movements, including rival movements.
This is easiest to see with rivals since they are displayed on the map. Get near one and refresh your map to see the rival icon move.
Rivals (and all machines in that matter) will stop moving from time to time though. E.g when they are scanning POIs, waiting for their mates or when they happen to get stuck.
Another way to get your rival located (and the easiest), is quitting to Main Menu and then Continuing your game. That generates new machine seed with machines in different locations, including rivals.
For 3rd method, aggro a seeker within Rival’s hearing distance (about 250m) or drop comm array lure to the ground.
4th method is to aggro a rival and running away, so that it follows you. Easiest to do with runners/hunters but more difficult with harvs/tanks due to their slow movement speed.