@MilanMi 

Hi, welcome to the community.
Here are the troubleshooting steps:

1. Ensure no VPN or network proxy is enabled on your phone, as these can interfere with app connectivity.

2. Change the DNS server on your Deco: How to Change DNS Settings on Your TP-Link Deco 
After updating the DNS server, reconnect your phone to the Deco network to ensure the new DNS settings take effect.

3. If your Deco has subscribed to the Security+ service, please check if YouTube or Gemini is being blocked there.

4. Check Parental Control settings: Set up Parental Controls with TP-Link HomeShield
   • Review your Parental Control settings in the Deco app
   • Verify that content filtering and website blocking are not accidentally restricting these apps
   • You can remove your phone from the Parental Control profile for a try.

Best regards.