Welcome Vishal1637_9,
Check for any outages: Apple - Support - System Status
(There hasn't been an issue reported on System Status recently.)
Have you tried using another Wi-Fi network yet? If not, we'd try that or disable Wi-Fi altogether and use the cellular network to try submitting the refund request: Request a refund for apps or content that you bought from Apple - Apple Support
Keep in mind, you don't want to use a VPN or security software on the device, as these may cause issues with connecting to Apple's servers: Check VPN (Virtual Private Network) and third-party software to help resolve network connectivity issues - Apple Support
If the issue continues to occur, does this only happen when you request a refund for this specific content or purchase? Does it occur with other purchases?
Wishing you well, cheers.