I think you'll find that there was a
Stockport-Euston non-stop, which ran both pre-Covid and after the resumption of more regular services this year, although it no longer runs and won't do so again for a while.
There was no Piccadilly-Euston non-stop ever, that I can remember. (OK, not since 1977, which is probably the extent of my memory, except on special occasions of course)
The Runcorn-Euston non-stop ran today (
https://www.realtimetrains.co.uk/train/Y30562/2020-12-17/detailed) and may continue to do so.