you left your dog when you go on the vacation, and he is probably mad at you for leaving him. my advice would be to spend time with him, play with him. do some training with him and reward with treats. you need to build trust with him again.
my friend was sad when she came to pick up her dog from my house one day because her dog was ignoring her and kept coming to me instead. so i gave my friend the treats and told her to do some commands with her dog, like sit down,...etc.. to get the dog's attention.
hope this helps.
