I would deffo protect again this year. My mother-in-laws went like that this year then after watering daily "boom" there they were. However that never happenned until atleast late july begfinning of august. It was a tad late for the fronds to uncoil but they were there.
Dont give up just yet. Wait again until next year and then if nothing then simply use it as a feature in the garden as the trunk still looks good as it is with or without fronds. Sometimes the frond can be a tad late. I suppose they get sloppy and tired as we do. lol x

I'd protect it as well - if it comes through the winter, when we get to mid/late April, try pouring a sugary water solution into the top - that sometimes encourages the plant to put out its fronds.