Trados 21, Check Spelling, language not supported

Hi

I am using Studio 2021, I usually translate into British English, but I'm currently translating into US English, and in this project the spell checker won't work, the Check Spelling is greyed out, language not supported. I have tried both Hunspell and MS Word, and I also have US English installed as a proofing language in MS word. When I check Hunspell, and go to custom dictionaries, I can only see one dictionary, CUSTOM.dic. Spellcheck works fine for my other projects into British English. 

Any ideas please? 

emoji