I had omitted the iterator variable on the body template. I had

<ng-template pTemplate="body" let-release>
  <tr [pSelectableRow]>

where I needed

  <ng-template pTemplate="body" let-release>
    <tr [pSelectableRow] = "release">

I should have put more of the p-table code on the question. This did work before the framework upgrade. I edited it for other reasons and introduced this. Thanks anyway