My name is ***** ***** I’ve been involved professionally with dogs in the health and behavioral fields for over 18 years. It will be my pleasure to work with you today.
Often when this occurs, it is because the dog pause after walking through the door and it came back and slapped her in the rear. It frightens them when that happens and they tend not to want to go through again. There are a couple of ways of approaching this. One is to use exceptionally good treats to tempt her to at least go out the doggy door. If she stays out, at least she isn't eliminating inside. Hot dog slivers and chic***** *****vers are high value treats and most dogs will go through for them. First have her go through with the flaps up and reward with the tasty treat. Be sure it is just a tiny amount of the treat since you don't want her getting full.
Once she realizes that you have treats, she should come through the flap to get the treat. You will want to bring her back in through the regular door and go back out so she is going out over and over again for the treat. Maker her desire for the treat overcome her fear of the flap. Some trainers will recommend leashing her and feeding the leash through the opening and coaxing her that way. I don't because I've found that can make the dog fear the door completely.
Another option is to house train her to ask to go out. Put a bell or other noise maker on the door low enough for the dog to reach. Each time you take the dog out, ring the bell. The dog will associate ringing the bell with going out and one day ring the bell to signal to you that she needs to go out. This may be an alternative to the doggy door for her.
Some owners replace the plastic flaps with cloth flaps while getting their dog used to coming through once again. Crate training can help as well.
I hope this information is helpful to you. If you would like any additional information or have more questions please don’t hesitate to press the reply to expert or continue conversation button so I can address any issues you still have . If you do find this helpful, please take this opportunity to rate my answer positively so I am compensated for my time.