Symbolic difference equation system

I'm trying to solve a system of differences equations in a symbolic way:

syms Y(t) A(t) K(t) S(T) I(t) N(T) delta lambda s theta gamma alpha
eqn1 = Y(t) == (1+alpha)^(t)*K(t)^theta
eqn2 = K(t+1) == (1-delta)*K(t) + I(t)
eqn3 = S(t) == s*Y(t)
eqn4 = S(t) == I(t)
eqn5 = N(t+1) == (1+lambda)*N(t)
sol = solve(eqn1,eqn2,eqn3,eqn4, delta,'IgnoreAnalyticConstraints',1)

I get the following error message:

How could I solve the problem?