Jade Wang ( A Google Employee) has answered in Google Business group help forum is that sometimes when you are not able to add some more lines in reviews, it may be because of Characters Limit.
He said –
@Juliette, I think you may be hitting a character limit for reviews (~4,000 characters). I know you spent a long time on the review, but is there a way you could try to cut it shorter and see if it will post?
So if you want to review any Business, you need to write down below 4,000 characters.