PRTB registration - PPS numbers

Hi guys
I wonder if any of you might have some useful advice for me. I am letting my house through an agency to 4 tenants. The previous tenancy was registered with PRTB, however, I haven't been able to register the current one because the tenants didn't fill in their PPS numbers. This was quite a while ago. I asked my letting agent to get the numbers several times and was told that as the tenants were new to Ireland, they didn't have the numbers yet, this has dragged on and on. At one stage the agent muttered something that one or two of the tenants did give him their numbers and that he'd email them to me. That didn't happen. Anyway, one or two numbers isn't enough, I need them for all tenants.
At first the agent advised me to send the form in to PRTB anyway which I did but it was returned as incomplete. That was a few months ago. I'll admit that as I haven't heard from PRTB since, I haven't been pestering my agent lately but I'd be much happier if I could register with PRTB and not worry about it.
I wonder if anyone else had similar problems and what you did about it.
Any advice is appreciated

We had a similar situation. No PPS no. as tenant was not Irish. Sent the form into PRTB anyway as somewhere in their blurb they said to enter PPS nos. if possible. The form was returned to us. We rang PRTB and said we wanted it on record that we had tried to register the tenancy (in case of fines etc.). They date stamped your letter I presume. We simply posted the form back to them again with a letter explaining the situation and they accepted this. They really just want you to make the effort and register.