There are too many potential causes for the winter demise of an ornamental grass to diagnose over the internet. It's safe to say the plants with a few new blades are not entirely dead, but I'd guess they are close. Those with no growth this late are probably done for. You might try dividing out the healthy perimeter sections of the grasses which are sprouting, but it sounds like that might be a lot of work for little benefit.

Some causes of winter death of OGs:

Too cold. 'Morning Light' is hardy to at least your zone, but you're near the bottom of the range. If the plants were grown in greenhouses, or field grown in much warmer climates, they may not have been properly acclimated when you got them. Plants like this would grow fine in their preferred season, but might not be able to withstand your winter.

Wet feet. These grasses do not like to have wet feet in winter. If drainage is not optimal, and your winter is wetter than usual, it could easily do them in.

Rootbound. If the plants were heavily rootbound, and you did not tease them out when you planted them, they could have strangled themselves, and never got fully established in your soil.

There are other causes, like insect damage, or burrowing critters, but the fact that all of your plants were affected leads me to believe it's one of the three I listed.

All that said...I'd probably wait another month before making any decisions. I have no idea where you are, or how warm/cold/wet/dry your spring weather has been. If the cut-offs in the center of your clumps can be easily pulled out, they've rotted, and that section will not send up new shoots.

Thank you so much for your help!! Hopefully the slow-growth ones will start to take off and I'll replace the ones with no growth soon. Thanks again!!

Cheyenne, WY. (6,000' elevation) Planted four clumps of Maiden Grass last June. They were 3 to four feet in height. Beautiful though the summer, fall and winter. Cut them back recently per directions on the care and maintenance card. It is now coming up to late May, and no sign of life whatsoever in any of the four. We have had a cold and wet spring. How long should I wait before giving up and replanting? If I replant, any suggestions for a different grass?

"Maiden Grass" is one of several common names for Miscanthus sinensis, and there are hundreds of cultivars of the grass. A few are hardy to zone 4, but most are not.

Try tugging on the stubs of last year's stalks, and see if they feel tight, or pop right out, looking all rotten at the base. If the latter, at least that section of the grass is dead.

Check out bluestem, linked below. They specialize in grasses for cold climates, and have a comparative chart full of information about grasses for your zone.

Here is a link that might be useful: Ornamental Grass Comparative Chart