If you haven’t been paid, speak to your agency and umbrella employer directly to find out why.
Mistakes can happen, and if you haven’t been paid then you need to know why as quickly as possible. Make sure you’ve followed your umbrella company’s processing procedure in full (i.e. has your time sheet been submitted and authorised in the right way?)
It may be as simple as this. But if you can’t find an obvious reason, you should liaise with your agency and your umbrella employer to work out what has gone wrong.