New Note 9 having trouble receiving and sending messages to one contact

[sherrieg33]

Hello all.  I got a Note 9 Feb 1, 2019. It was working fine and now suddenly has had issues with texting one contact. We will be texting fine then the messages just stop. They have a galaxy 9+. It is only working intermittently. The messages appear to be sent on both ends with no failed message symbol, yet we don't recieve them. Signal bars are good and had happened in different locations. My Note also locked me out about a week prior to this texting issue. It wouldn't accept my swipe to unlock and did a factory reset. Afterwards, I reloaded all my info back on the phone.  All other contacts work for texting, the other person uses Sprint.  I have tried to restart, did a soft reboot, cleared the cache and data on the messaging app. Any ideas? It's so frustrating. Hope I didn't purchase a lemon of a phone.