Hi  @shiva9525-_,

TL-WR850N is a customized device specifically designed for local Service Providers. Its software is tailored to meet the unique requirements of these providers, ensuring alignment with their specific needs. While our technical support team is adept at providing general guidance and suggestions for products with standard, generic firmware. However, due to the specialized nature of the firmware on your device, our ability to provide troubleshooting may be limited.

TL-WR850N supports WDS bridge function, you can consider enabling it:

https://service-provider.tp-link.com/wifi-router/tl-wr850n/#specifications 

We recommend contacting the technical support of your Service Provider who supplied the device, as they are best suited to provide the necessary assistance for your device.