This could just be an age thing where they seem to forget all their training. You could try practising the recall at home with either something really tasty that he only gets for this exercise or a special toy that again will only be used for recall training. When your in another room, call him to you and when he comes give him his reward. Practise this over a few sessions until he is consistent. When it comes to going out, put him on a training line so he still has the freedom but you are still ultimately in control. Call him to you and when he comes, reward and send him off to play again. I know some people have success with walking in the opposite direction but when i did that, I could swear Vegas was standing there going "see ya"
The fact he was doing it before is encouraging and going back to basics will probably solve the problem. If you see him running off, dont continually call him if you know hes not going to pay attention to you as he will end up no longer associating the command with returning to you. He'll just think "come" means go off and do your own thing
Good luck