When Apple Watch is synced with my iPhone, I don’t get audible notification of arriving texts. Why?

In my experience the apple watch notification system is and alway has been very buggy.

On watch OS4 a good old restart of both devices usually fixes the notification issues.

Watch os 5 seems a bit worse, turning on and off silent mode / theatre mode on the watch and phone can fix notifications (for a while).

Also try turning off notifications in the watch app on the iphone, then turning them on again a few minutes later might help. As I said in my experience, these notifications have always been a bit of a buggy / unstable feature hopefully they will get round to giving it a fix in a later update.

1. Swipe up for control center and check things like Silent mode are not enabled.

2. Compare observed behavior with Apple’s official description in https://support.apple.com/en-us/HT204791

For DIY fixes the users here have thousands of eyes and a combined experience way greater than Apple’s paid support techs. You have been through most of the obvious fixes, but it is worth trying a forced reboot (press and hold both buttons until the apple logo appears and the watch begins to restart. If that doesn’t help, hit link Contact Apple Support and ask the previously mentioned paid techs.