CNN – One of the most sought-after toys of the holiday season is leaving some kids disappointed.

Some parents said the “Hatchimals” their children received on Christmas morning will not hatch.

The toy is supposed to “hatch” from an egg when children knock, tap, or rub on the shell after about 30 minutes of playtime.

The Hatchimal inside responds with lights and sounds and eventually hatches into a creature kids can talk and engage with.

It was a tough find for many parents during the holiday season, with it selling out quickly in stores.

Unhappy customers are airing their frustrations with the toy on Twitter.

Parent company Spin Master is urging customers to contact them via direct message on Twitter, but tweets show it’s been difficult to get a response from the brand.

Spin Master did not respond to requests from CNN for comment.