Why isn't a new account added in Thunderbird with TorBirdy added in Tails?

I want to add a new account to Thunderbird with TailsOS. Torbirdy is added to Thunderbird. And I couldn’t do that if I wanted to add email accounts with .onion and .org domains respectively. Why can’t it? please tell me.

Please provide screenshots, error descriptions, or more details in general. Otherwise, it will be very hard to help you.