After reviewing the forums, I’ve: 

• made sure the form is published
• ensured question and fields and Airtable and Typeform is exactly the same
• used Multiple Choice in Typeform and multiple select in Airtable (i’ve also tried single select)
• checked there are no extra space or duplicate characters

but am still getting the hmm...not a perfect match error message. Driving me insane, all the other fields have been able to sync properly.