Why are my pink pampas grasses not growing??

Question

We’ve cut them back in the spring, and now nothing, no sign of any green.

Answer 1

You are in planting zone 6a and the planting zones for pampas grass are 7 to 11. So it is possible it just froze out during the winter. Also, you may have experienced a dry winter, and without supplemental watering, you can lose plants.

Here is general care for pampas grass, you might see another reason it didn't come back:
https://www.gardeningknowhow.com/ornamental/foliage/pampas-grass/growing-pampas-grass.htm