OnePlus
Resend Undelivered Messages Automatically auf OnePlus
When a text fails to go through on a OnePlus phone, the reason is usually a dropped data or carrier connection at the exact moment of sending. Instead of just showing an error, OnePlus Messages has a built-in fallback: it can automatically retry the message as a regular SMS.
This behavior is controlled by Resend messages if undelivered, tucked inside the chat settings rather than the main app settings, which is why most people never find it.
To check or change it: Open the Messages app ➔ Open the menu ➔ Open the Settings ➔ Tap on Chat features ➔ Tap on Resend messages if undelivered ➔ Choose an option.
From here you typically pick between Always resend as SMS, which sends the fallback automatically without asking, and Resend as SMS with a prompt, which asks you every time a message fails before it retries.
Automatic resending is useful if you send a lot of messages over a weak signal and do not want to babysit every failed send. The prompt option makes sense if you are on a limited SMS plan or roaming, since SMS fallback can incur extra charges depending on your carrier.
If messages still fail after changing this setting, the problem is more likely a network or carrier issue than a Messages app setting, and switching networks or restarting the phone is a better next step.