How to Fix Error Code REG99, REG91 or REG09 Unable to Connect on T-Mobile

Calls over WiFi are now the new future and if you’re a T-Mobile customer, chances are you’re pleased to learn that the network now implements WiFi Calling.

Unfortunately, some customers are airing their annoyance about encountering error codes REG99, REG91, and REG09 that prevent them from connecting. If you’re having the same issue on T-Mobile, don’t get too frustrated just yet.

Image credit: T-Mobile

Solutions to Resolve T-Mobile Error Code REG99, REG91 or REG09

Here are a few things you can do to get rid of these error codes.

Update Your Smartphone to the Latest Version 

WiFi calling on some smartphones requires the use of the latest version of the operating system. One of the first things you can do to fix the issue is to check if your phone has a pending software update.

If there is, make sure you download and install the newest version right away. Once the update is completed, restart your device to see if the error code is gone.

Enable WiFi Calling

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In case you don’t know it, you can set some WiFi networks to block all forms of VoIP traffic, and this includes WiFi calling. But if you don’t own the network, there’s nothing you can do about it.

While you can raise your concern with the network administrator, they still have the final say on this.

If you’re the WiFi network owner, simply refer to the manual of your router to learn how to unblock WiFi calling. Learn how to enable VoIP traffic through the router and disable features that can affect VoIP services.

The WMM can also be turned on if it’s supported by your router to ensure a faster performance for your WiFi calling feature.

Restart Your Router 

WiFi calling might be affected if you have a malfunctioning router. Your smartphone won’t be able to communicate with the T-Mobile network which may result in error codes REG99, REG91, or REG09.

To fix this problem, a simple reboot may do the trick. After the restart, reactivate the WiFi calling to check if the issue is gone.

Get a New SIM Card on T-Mobile

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Several users have claimed that T-Mobile told them to request a new SIM card so they can take advantage of the WiFi calling feature. This works since there are older SIMs without WiFi calling support. Getting a new SIM that supports the WiFi calling feature may help fix the issue.

You can contact T-Mobile support to require a new SIM card or you can also personally visit any of their physical shops. Once you have your new SIM, proceed to activate it on the T-Mobile network. Here’s how to do it:

  1. Use your T-Mobile ID to log in to your account.
  2. Choose the specific line where you want to add your new SIM.
  3. Proceed with the security verification.
  4. Choose either eSIM or physical SIM.
  5. Enter your EID or ICCID when prompted to.

Proceed to the Settings app and turn on WiFi calling after your SIM is activated.

T-Mobile error codes REG99, REG91, or REG09 unable to connect issue can be very annoying so make sure you follow the tips and tricks above to fix the issue right away.


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