Whipping cream that has been frozen won't whip I have whipping cream that has been frozen; it is now separated and won't whip. Is there anything I can do to make it whip?
Sorry, no. 

Whipping cream that has been frozen is perfectly fine to use in many dishes, but it won't whip.

As far as I know, this is irreversible, so no, you can't make the cream "whipable". If you are very lucky, you will get it to a sort of semi-stiff stage, but nothing that would be suitable for cake decorating or similar.



Not part of your question, but possibly interesting for next time:
Whipped cream can be frozen, so if you have leftovers, you could pipe little tufts or similar, freze them and use them to decorate desserts.