Unable to solve the collocation equations

global phi rhos rhof cps cpf ks kf Pr lambda l Bv Bt Ec Hs gamma Q A1 eta
f=[
    y(2);
    y(3);
    lambda*y(2)-(1-phi)^2.5*(1-phi+phi*(rhos/rhof))*(y(1)*y(3)-y(2)^2)-(1-phi)^2.5*(Q*exp(-A1*eta)+l*Bv*(y(7)-y(2)));
    y(5);
    (kf/((ks+2*kf-2*phi*(kf-ks))*kf)/(ks+2*kf+2*phi*(kf-ks)))*Pr*((1-phi+phi*(rhos*cps/rhof*cpf))*y(1)*y(5)-l*Bt*(y(8)-y(4)-l*Bv*Ec*(y(7)-y(2)-Hs*y(4))));
    y(7);
    y(7)^2-Bv*(y(2)-y(7))/y(6);
    -gamma*Bt*(y(4)-y(8))/y(6);
    ];

res=[ya(1), ya(2)-1,ya(4)-1,yb(2), yb(4), yb(6)-yb(4), yb(7), yb(8)];