My dog Nina, mini french bull dog

Question
Nina has always junped on the couch with no problem.....she is three years old....tonight I notice she  cant jump up on the couch, she eats drinks goes to bahtroom normal,,,,,in no pain..walks up and down steps and even runs.....but wont jump on the couch.  She trys but can't, does not limp......please can you help.

Answer
If your dog suddenly cannot jump up on the couch after she always did before, there is undoubtedly something wrong... most likely in her back. I would try to get her into a veterinary chiropractor if you can find one in your area. A good one is worth his/her weight in gold.
http://www.avcadoctors.com/search_for_avca_certified_doctor.htm

Watch your dog for these signs:

She should always do full stretches, both front and rear.
She should do full yawns.
She should be able to turn her head easily in both directions and touch her ribs.
Her spine should look straight from the back of her head all the way down to the base of her tail. (If she had a normal dog tail, that should hang/be carried straight also, but, of course, it won't since she is a French bulldog.)
Make sure she is carrying her weight equally on all feet when she stands.

If your dog is not able to complete any of those, she definitely has a problem.