Твоё is informal singular neuter.
Ваши is plural (the objects that are yours) when in English you would use singular 'your' in formal occasions (or 'thine' in outdated speak) or plural 'your' (when speaking to several people).
It could have been a typo, if you intended to write твои. Sometimes it is difficult for the algorithms to distinguish between a typo and a wrong answer.
I was marked correct using the masculine singular form of "your", is that right?
"Где твой тетради?" Should I report this for accepting an incorrect answer?
in gave me that option as a multiple choice, I selected it and got it wrong. I see now that the last letter is technically different, but didn't notice. So, it looks like they used your sentence to trip me up!
In this sentance are they referring to several Notebooks for one person or like a teacher asking a class "your notebooks class" vs an idividuals notebooks(more then one type deal)