I have checked and unfortunately this extension can no longer work apart from that in the English language.
The extension was based on the api of this repo: freeDictionaryAPI/modules at master · meetDeveloper/freeDictionaryAPI · GitHub to which the author has removed all the dictionaries except the English one.
For those who need Google dictionary I can recommend this other extension
[Free] Dictionary Extension : Make Dictionary Apps easily
However, I don’t know which api this extension is based on and if it works