This is an Irish to English exercise. That means that you will only be entering an answer in Irish for a "Type what you hear" exercise, and, as the speaker didn't say Tá muid, you have obviously misheard her if that's what you wrote.
"Type what you hear" exercises only accept what is in the speakers script as a correct answer - they don't allow for alternative answers.
If this was an English to Irish exercise, and you were asked to translate "We are and they are" into Irish, Tá muid would be accepted.
Given the difficulty of distingishing tá muid and táimid, they probably should not use these exercises for "Type what you hear" exercises, but to the best of my knowledge, that type of exercise only allows for one specific answer.
táimid is not a contraction of tá muid - it's not the equivalent of "they've". The synthetic forms are distinct verb forms
I am getting errors in the type what you hear also. The speaker only says part of the phrase, then when I choose what I have heard the program tells me that I made an error. I have tested this with others for their opinion. Very frustrating........and probably confusing?
No, tá is the "to be" verb ("is" in English)
When you are conjugating verbs, siad is used in the third person plural conjugation. The "they" conjugation. In this case, "they are."
I am = táim You (singular) are = tá tú He is (also used for masc. nouns) = tá sé She is (and fem nouns) = tá sí We are =táimid You (plural) are = tá sibh They are = tá siad