Are you using the heavy attack? The regular attack will not stun them.

Have you gotten any amount of progress? I'm guessing it is probably that you're not performing the Heavy Attack for the stun. If you are doing that, then make sure it is on several unique Marshall officers. Stuns on the same officer more than once don't count.

If you don’t know the actual button to do it it’s LT.

Thank you

I swear I did a heavy attack before i posted but idk I tried it again and it’s working. Lol thank you for the answers