Error Message?

I am trying to use part of the amount I carried from a previous year in my RRSP to pay my HBP back, and it is saying I can't do this even though I am pretty sure I should be allowed. 

 

Andrew: You have unused RRSP contributions from prior years and you have designated RRSP contributions as your HBP and/or LLP repayment. Any portion of RRSP contributions made in 2018 or before cannot be designated as HBP/LLP repayments.

 

Does anyone know why? Is this really not allowed? 

 

Thank you, 

 

Andrew