According to the documentation, "Manipulate only "notices " explicit visible parameters:"
http://reference.wolfram.com/language/ref/Manipulate.html
You've defined the function fb to take one parameter argument, Fc_. The other parameters are not explicity visible in fb.
If you redefine fb as
fb[Fc_, a_, \[Theta]A_, \[Theta]B_, \[Theta]C_, \[Tau]_, cA_, cB_, cC_, b_, p_, \[Beta]_] := ...
and call it as
Manipulate[
Plot[fb[Fc, a, \[Theta]A, \[Theta]B, \[Theta]C, \[Tau], cA, cB, cC,
b, p, \[Beta]], ...
then the other parameters will have an effect.
