Learn how to troubleshoot Wi-Fi Calling problems. If you have an Android phone and you use the Wi-Fi Calling app, see Wi-Fi Calling troubleshooting for Android.
When you try to change the call forwarding or call waiting settings using Wi-Fi Calling, you may see on your screen, "Network or SIM card error." When you're actively using Wi-Fi Calling, the call forwarding and call waiting settings cannot be changed.
To resolve this issue, simply change the settings when you're not using Wi-Fi Calling, You can also use short codes to change call forwarding and call waiting settings.
If you're using Wi-Fi Calling, and the other party is using Wi-Fi Calling as well, you may notice issues with receiving incoming calls and with incoming calls not forwarding to voicemail.
To resolve this issue, visit the Phones page and select your device. Then, click the SOFTWARE UPDATE button and follow the steps to update to the latest version.
This message displays when your phone is having trouble connecting to the Wi-Fi Calling service.
You might see alternate versions of this error, such as:
To resolve this error, turn off Wi-Fi for 1 minute. Then, turn it back on and try to use Wi-Fi Calling. Visit the Phones page, and select your device. Look for Wi-Fi Calling to access guided steps. If you still see the error, contact T-Mobile Customer Service.
This message displays when the SIM card has not received a needed SIM card update. This update is automatically sent from the network after a SIM card or phone number change has been completed. To resolve this issue, make you're in T-Mobile coverage and contact T-Mobile Customer Service. Customer Service can send the SIM card update to you.
The REG99: Unable to Connect error may appear when Wi-Fi Calling is active and connected to certain routers or devices and is usually caused by the following:
If you're experiencing dropped calls, have audio quality issues, or have trouble with Wi-Fi calls, it could be due to a Wi-Fi issue or a phone problem.
To resolve this issue:
If you're experiencing messaging issues, it could be due to a Wi-Fi issue or a phone problem.
Wi-Fi calling errors display when there are problems connecting to Wi-Fi, or when there is a problem with the Wi-Fi Calling service.
Scroll to the error for steps to fix the problem.
If Wi-Fi Calling still doesn't work, visit the
Phones page, and select your device. Look for Wi-Fi Calling to access guided steps.
If you still see the error, contact T-Mobile Customer Service.
To resolve this issue, contact us.
SIM not ready
Unable to Connect
Most devices will show REG99: Unable to Connect.
Error can appear in the following cases:
Most devices will show ER01: Invalid Certificate.
Appears when mutual authentication between the device and the network fails.
Typically a transient error that will fix itself.
Most devices wil show ER01: Invalid Certificate.
Certificate is expired or issue exists with certificate verification server.
Same as ER010
Missing 911 Address
You must plug the modem directly into the router, with no other routers or devices in between. This is required for network traffic to be directed correctly.
They must allow DNS lookups through the firewall. These are IPv4 blocks registered only to T-Mobile.
Wi-Fi Calling troubleshooting for Android
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