Hello. I am sorry to hear that Clutch is having some trouble with the pet sitter. My name is ***** ***** I would be happy to help.
I can tell you that having owned and operated a pet sitting business for many years this is not uncommon behavior. For Clutch he is just trying to protect his house. At his age he may also have some cognitive dysfunction going on which is similar to dementia in humans.
There may not be much this pet sitter can do if Clutch has decided that he does not want him in the house. A few things he could try is offering him a treat and talking to him calling him by name when he comes in. He could try taking a female friend over with him and see if she gets a better response.
I know this is difficult but we would not want to try any type of sedative at his age without you there and we do not want Clutch or the pet sitter to get injured. Now if your vet knows Clutch well you could call them and they may be willing to give something like Xanax or Valium to help calm him down.
There are over the counter calming tablets and calming collars that can be purchased at most pet stores that work well. A final option would be Melatonin but this can take a few days to really change this behavior. A small dog can have 3 mgs per day a med-large dog 6 mgs per day. If he wants to try the Melatonin make sure he gets one that does not contain Xylitol.
The over the counter products do work but may not be enough for Clutch so I would give your vet a call and explain the situation and see if they can call something in for him.
I wish there was more I could do to help. Please reply back if you have additional questions and I will be happy to continue. If you have no additional questions please take a few moments to provide a rating so that I am compensated by justanswer for assisting you.