Was this problem a board you printed with the Voltera or a commercially made board?
This happened to me three days ago when I wanted to put down tin-lead paste that I just received earlier in the week from Voltera. It was to go on a commercially made board (tin-lead, not lead free.)
The machine was squishing out paste but it just would not stick.
I cleaned the board with acetone a few times, wiping with paper only one direction. Started over and then the paste stuck properly.
I don’t know if the acetone cleaning did the trick or if it was a coincidence.