Thanks! This pointed me in the right direction to fixing the issue. I was dealing with the issue on 3 devices, my new iPhone XS, an iPad, and my MBP. The steps I took were to:
1. Sign out of iMessage on all three devices (I didn't just toggle it off, I went to "you can be reached at..." and from there tapped "sign out of iMessage" on the iPhone and iPad, and went to preferences -> sign out on the MBP.
2. I then toggled off iMessage on both the iPhone and iPad and also confirmed that iMessage was turned off under iCloud settings.
3. Then I restarted all three devices
4. Then I toggled iMessage back on on the iPhone, and signed in, and made sure iMessage was turned on in iCloud settings.
5. I then confirmed my "you can be reached at..." addresses were JUST my phone number and my main iCloud email.
6. Once everything was good on my phone, I turned iMessage back on/signed in on the MBP and then the iPad. (6a I found a conversation with a "failed to send" message on my iPad, I deleted this conversation from the iPad).
This worked for me, I can now send and receive text messages and have them sync across all my devices again.