I am not a Materials Studio user, but I suggest you only enable the LDA+U option. You must verify that a U value appears in your output.

You must enable the LDA+U option during the calculations. This is because the Hubbard 𝑈 correction is specifically applied within the LDA+U (or GGA+U) framework. Without enabling LDA+U, the system will not recognize or apply the Hubbard 𝑈 values you have set. The LDA+U method modifies the exchange-correlation functional to account for the on-site Coulomb interactions for localized 𝑑 or 𝑓 electrons, which is crucial for transition metals.

After enabling LDA+U, you should indeed adjust the Hubbard 𝑈 values in the Electronic Configuration section of CASTEP. This is where you specify the 𝑈 parameters for the specific orbitals of the transition metal atoms in your system. These values are typically determined from literature or by fitting to experimental data.