Question: Problem with plot

hi all

i have this code and want to plot(NphiB1,y). but it is not plotted.

help me plz

restart:
nB0:=1:
hb:=6.63*10^(-34):
aB:=1/(3*(3*nB0*Pi^2)^(1/3)):
gB:=4*Pi*aB/mB:
xiphase:=1/sqrt(4*mB*gB*nB0):
qcB:=8.26*10^(-3)/xiphase:
qB:=y*qcB:
v1:=-gB*nB0:
v0:=4*gB*nB0:

L:=1.5*xiphase:
k2:=sqrt(qB^2+2*mB*v1):
k3:=sqrt(qB^2-2*mB*v0):
beta:=k3*L:
W:=2*cos(beta)*(qB/k2-k2/qB):
Q:=sin(beta)*(qB/k3-k3/qB+qB*k3/k2^2-k2^2/k3/qB):
P:=sin(beta)*(qB/k3-k3/qB-qB*k3/k2^2+k2^2/k3/qB):
theta1 := -arctan((Q*(-P*Q+sqrt(Q^2*W^2+W^4-W^2*P^2))/(Q^2+W^2)+P)/W):
b1:=(theta1+k2*L)/(2*k2):
Stheta1 := -(Q*(-P*Q+sqrt(Q^2*W^2+W^4-W^2*P^2))/(Q^2+W^2)+P)/(W*sqrt(1+(Q*(-P*Q+sqrt(Q^2*W^2+W^4-W^2*P^2))/(Q^2+W^2)+P)^2/W^2)):
Ctheta1 := 1/sqrt(1+(Q*(-P*Q+sqrt(Q^2*W^2+W^4-W^2*P^2))/(Q^2+W^2)+P)^2/W^2):
phiB1=evalf(-arctan((1/4)*(cos(2*qB*b1)*(sin(beta)*(-qB/k3-k3/qB+qB*k3/k2^2+k2^2/qB/k3)+cos(theta1)*sin(beta)*(-qB/k3-k3/qB-qB*k3/k2^2-k2^2/qB/k3)+2*sin(theta1)*cos(beta)*(-qB/k2-k2/qB))+sin(2*qB*b1)*(4*cos(theta1)*cos(beta)-2*sin(theta1)*sin(beta)*(k2/k3+k3/k2)))/(-sin(2*qB*b1)*(sin(beta)*(-qB/k3-k3/qB+qB*k3/k2^2+k2^2/qB/k3)+cos(theta1)*sin(beta)*(-qB/k3-k3/qB-qB*k3/k2^2-k2^2/qB/k3)+2*sin(theta1)*cos(beta)*(-qB/k2-k2/qB))+cos(2*qB*b1)*(4*cos(theta1)*cos(beta)-2*sin(theta1)*sin(beta)*(k2/k3+k3/k2))))):
NphiB1:=evalf(phiB1/Pi);
#SNphiB1:=simplify(NphiB1);
plot(NphiB1,y);