Hi,
Hopefully you had already figured this out in the meantime, but it appears that you did not select anything for 'data to filter'. So you have your filter source, the user table, but then you also need to specify on which field you want to apply that filter! So you could for example use 'user' to filter 'assigned to'. But it seems that in your case you need to use a cascading filter. Configure a Single/Multiple select or cascading filter in the in-line editor