SMS Read Status of Messages Not Syncing Across Devices

When I read text messages on my iPhone sent from non-Apple users, the read status is not updated on my iPad. These messages show as unread on iPad. This is not an issue with iMessages. I have the latest versions of iOS on both devices - 15.4.1. I have restarted both devices and also logged out of iCloud and logged back in several times. I also turned on iCloud for Messages, which is something I have never had turned on in the past. I don’t believe this is relevant, but I also have the latest Apple Watch which is also up to date..