This petition was rejected

The Government e-Petitions Team gave the following reason:

We understand that you want Esperanto to be made an "official language", but we're not sure exactly what new status or requirements you want the Government to introduce regarding this language.

You could start a new petition explaining clearly what you would like the Government or Parliament to do. Additionally, the Government would only be responsible for any policy related to reserved matters, and not matters that have been devolved to Scotland, Wales and Northern Ireland.