I apologise if this is posted in the wrong area, if I have duplicated the post.

I am flying with Malaysian airlines on Tuesday morning. Tried to online check in today but when I come to complete my child's date of birth, I get a message saying it is invalid.
I tried checking in with the app and his year of birth (2013) is not an available option.
Is this standard procedure because of his age and we will be expected to check in at the airport instead?

Many thanks 🙏🏼