Question: Pdsolve do nothing

Good morning, I've tried to solve this pd-eqn with pdsolve, but there is no output (not solution nor error) and the promp goes on the next row

 pdsolve(6*cos(theta)^2*C^2*(diff(f(theta, `ϕ`), `ϕ`))^2*c^2+A^2*omega^2*cos(theta)^4+6*cos(theta)^2*C^2*(diff(f(theta, `ϕ`), theta, theta))*(diff(f(theta, `ϕ`), `ϕ`, `ϕ`))*c^2+A^2*omega^2-2*A^2*omega^2*cos(theta)^2+6*C^2*(diff(f(theta, `ϕ`), theta, `ϕ`))^2*c^2-6*cos(theta)^2*C^2*(diff(f(theta, `ϕ`), theta, `ϕ`))^2*c^2-12*C^2*(diff(f(theta, `ϕ`), theta, `ϕ`))*cos(theta)*sin(theta)*(diff(f(theta, `ϕ`), `ϕ`))*c^2-12*cos(theta)^2*C^2*(diff(f(theta, `ϕ`), theta))^2*c^2+6*cos(theta)^4*C^2*(diff(f(theta, `ϕ`), theta))^2*c^2+6*C^2*(diff(f(theta, `ϕ`), theta))^2*c^2+6*C^2*(diff(f(theta, `ϕ`), theta, theta))*cos(theta)^3*(diff(f(theta, `ϕ`), theta))*sin(theta)*c^2-6*C^2*(diff(f(theta, `ϕ`), theta, theta))*cos(theta)*(diff(f(theta, `ϕ`), theta))*sin(theta)*c^2-6*C^2*(diff(f(theta, `ϕ`), theta, theta))*(diff(f(theta, `ϕ`), `ϕ`, `ϕ`))*c^2=0,f(theta, `ϕ`));

can anyone help me?

Thank you

S.