This issue was talked about in the Moss Ball care guide and Q&A article.
My moss ball not round anymore, why and what should I do?
It got squeezed in tank - cause a lot of them grow together. Or during shipping. Either 1. Roll it with hands. Or 2.Tight it up firmly as above for couple of weeks.
Here is how:
Roll it round gently until round.
Let it shape by itself in round for a few hours
Put it back in water
You: ???
Me: Yea yea. Just roll it.