Unable to reset DNS Server back to 'Use DNS Proxy' after setting once to 'Use below'. Please help.

Messages
15
Location
Prayagraj
ISP
JioFber
I set DNS server once to 1.1.1.1 and after unsatisfactory results tried to reset back to the default 'Use DNS Proxy' but it does not get saved. A popup occurs asking for valid Domain Name which was not applicable earlier.
 
Yea enter Google.com in domain name.