Text message alerts

There could be a couple of reasons. One could be that Hide Alerts is activated for one or more of your conversations. Open the Message app and look for a small "crossed out bell". out of the conversations. You deactivate Hide Alerts by swiping from left to right on the conversation in the overview and tapping the purple bell

The other could be that you have Do Not Disturb, or another Focus profile which activates automatically.

If Do Not Disturb or another Focus profile activates automatically, then a Schedule is active.

To disable or delete this schedule, go to:

Settings → Focus → Select Profile → find SET A SCHEDULE → Tap into the time → tap Delete Schedule or just deactivate.

You can read more about how to use Focus here:

Use Focus on your iPhone or iPad - Apple Support

Okay hehe. If you still find that your messages are missing sound, check my other advice about Focus.

Some Focus profiles, for example Do Not Disturb can have a Smart Automation, or Scheduled time where it starts automatically. This may cause notifications to be set to silent. It is not certain that this is the reason, but it could be one of them.

Thank you! You're welcome.