If the internet works perfectly on Wi-Fi but stops working when you switch to mobile data, it can feel confusing and frustrating. Everything seems fine at home, but the moment you leave or turn off Wi-Fi, apps stop loading. This is a very common situation and usually does not mean there is anything wrong with your phone or SIM card.
Below are the most common reasons this happens and what you can realistically do.
Reason 1: Mobile Data Is Disabled for Specific Apps
Some apps are allowed to use Wi-Fi but are blocked from using mobile data. When this happens, the app works fine on Wi-Fi but fails as soon as you switch networks.
What to do
- Open app settings and check data usage options
- Make sure mobile data access is allowed for the app
- Disable data saver mode temporarily
Reason 2: APN Settings Are Incorrect or Missing
Mobile data relies on APN settings provided by your carrier. If these settings are incorrect, outdated, or missing, mobile data may not work even though Wi-Fi does.
This situation is very similar to cases where mobile data appears connected but does not actually work.
What to do
- Go to mobile network settings and reset APN to default
- Turn mobile data off and back on after resetting APN
- Avoid entering APN details manually unless provided by your carrier
Reason 3: Weak or Unstable Mobile Network Signal
A phone can stay connected to mobile data while the signal quality is too weak to transfer data reliably. This is common indoors, underground areas, or crowded locations.
What to do
- Move to a different location and test again
- Turn Airplane Mode on for 20 seconds, then turn it off
- Switch between LTE and 5G to refresh the connection
Reason 4: VPN or Private DNS Blocks Mobile Data
Some VPN or DNS configurations work fine on Wi-Fi but block or slow down mobile data connections. This can feel very similar to situations where your phone says it is connected but has no internet access.
What to do
- Disable VPN temporarily and test mobile data
- Set Private DNS to automatic if it is manually configured
- Close the affected app completely and open it again
Reason 5: Carrier Restrictions or Temporary Network Issues
Sometimes the issue comes from the carrier side. Temporary outages, usage limits, or regional restrictions can affect mobile data while Wi-Fi continues to work normally.
What to do
- Check if mobile data works in a different location
- Wait a short time and try again
- Contact your carrier if the issue happens frequently
Quick Checklist
- Confirm apps are allowed to use mobile data
- Reset APN settings to default
- Test mobile data in another location
- Disable VPN or Private DNS temporarily
- Switch network mode and retry
When This Is Normal and When It Is Not
If mobile data fails briefly while Wi-Fi works, it is usually a temporary signal or network issue. If mobile data never works in multiple locations and over several days, contacting your carrier or replacing the SIM card may be necessary.