
When he used to recall well, what did you use to praise that recall? A tasty treat, a game with a fun toy or just a pat and a good boy?
If he's just got bored about obeying you or because he's a teenager and being awkward, probably the best thing to do is to use the long leash, make him come back to you if necessary, and make a big fuss of him, tasty treat, game with the fun toy, make coming to you the best thing since sliced bread. If you lose control of recall at this age, it can be difficult to get it back and you end up with a dog doing vanishing acts until its time for tea. Really work hard at that recall, make it fun and exciting and very rewarding.
Good luck.