Deposit Not Returned - Emails Unanswered

Hi everyone, looking for some more advice.

Recently went via TDS over what my previous LL wanted from the deposit, but agreed to £225 that he can keep and the rest (£375) is returned to me. However, he hasn't paid. I've informed TDS and they've said they'll give him a nudge but that i'll need to contact him too. I have done, and my emails are going unanswered.

We agreed via TDS to the deductions several weeks ago and that we should have been paid by now, so im asking what i do next if my emails continue to go unanswered?