Originally Posted by
SpookDroid Were the conversations with that person 'chat' conversations (i.e. another Android/Samsung device using RCS, but not Google's)? If so, that's why your messages cannot be accessed other than by the 'stock' app. Also, have you given the Messages app 'time' (about an hour) to sort/display all messages? Sometimes it takes a while depending on how large the message database is.
A lot of text conversations look to be with iPhone users, but I can't say that 100% of them are.
Yes, I've been using the phone for over a week now but no more messages have appeared in Google's app.