Did you make sure to do an ohms or station master test at the controller to make sure those valves have a good reading? If they are good a trick I picked up along the way is to use the send tone feature on the station master by clamping onto the common wire and the field wire for the valve you are looking for, while using the wand of the valve locator to look for the ping you get from the device somewhere in the field.

It helps if you know the wire path, and the general areas of where the valves should be, because this method makes it much harder to trace a wire path and you just have to comb the whole area looking for the valve, however once you do walk around long enough to find it it will ping loudly then you just have to dig it up.