Only receive reply notifications with group messages, but not with single message replies

[VAuthor]

When I send group messages, I'll get notified when someone replies. However, when messages are sent to only one person and they reply, i won't get notified of the reply. I've checked and double-checked all of my notification settings, and I believe they're all correct.

By the way, I had the same problem with my s6 after a software upgrade. My carrier is Verizon.