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# How can I troubleshoot a “PDP Authentication Failure” error on iOS?

A "PDP Authentication Failure" error means the eSIM cannot authenticate with the local network. The most common cause is incorrect APN settings or Mobile Data Switching being enabled.

###### Step 1: Check APN settings

Incorrect APN settings are the most common cause of this error.

1. Go to **Settings** > **Cellular** > tap your Stippl eSIM (**Secondary**)
2. Tap **Cellular Data Network** (or **APN Settings**)
3. Under **Cellular Data**, clear the **APN**, **Username**, and **Password** fields — leave them all blank
4. Restart your device

|| If you don't see "Cellular Data Network," your carrier may lock APN settings. Try Step 5 below.

###### Step 2: Turn off Allow Mobile Data Switching

1. Go to **Settings** > **Cellular**
2. Find **Allow Mobile Data Switching** and toggle it **OFF**

This ensures your iPhone routes data only through your Stippl eSIM.

###### Step 3: Verify your data balance

1. Open the **Stippl app** > **eSIM**
2. Confirm your plan is still active and has remaining data

###### Step 4: Manually select a network

1. Go to **Settings** > **Cellular** > tap your Stippl eSIM (**Secondary**)
2. Tap **Network Selection**
3. Toggle **Automatic** OFF
4. Wait for available networks to load, then select one

###### Step 5: Reset network settings

Go to **Settings** > **General** > **Transfer or Reset iPhone** > **Reset** > **Reset Network Settings**

This clears saved Wi-Fi passwords and VPN configurations, then forces your device to re-establish the network connection from scratch.

|| Still not working? Contact Stippl support with the email address linked to your Stippl account and we'll investigate.