I have zero cash in my account but won a few U dollars.
So I joined the $2 R&A $200 GTD [NV], knowing I have an extra bullet to rebuy, and another to add-on.
It doesn't say anywhere that you can't R&A with U dollars, but every time I try, it says, "The rebuy you requested is not available because there are not enough funds in your account."
Now I'm stuck playing this at a huge disadvantage. I would have played something else if I knew this to be the case.