Thanks for all the replies! After posting that thread my boyfriend and I tried again later that night. . . SUCCESS! It turns out that her anatomy is a bit skewed. She had her back injury before I adopted her 2 1/2 years ago. . . she was hunched a bit, so that caused her bladder lay above her stomach instead behind it.
Expressing her bladder takes two of us, I press her stomach out of the way and Zane expresses the bladder. Yeahye! I was so relieved.

And yes, I does help when we express her bladder right after her massage and exercises.

Thanks again

-Anu