My jack russell is 1 year old and is pooing in the house?

my dog was potty train from a very early age and she seem to learn very well she would bark at the back door to indicate she wanted to go outside, now all of a sudden she isn't letting me know and keeps pooing on the rug, I have tried everything, praises her with a training biscuits when she goes outside and have clean the rug of all odours so it would stop her going in the same place, please advise I am not sure want else I can do.