Site goes down after few minutes

Hi Guys I hope you all are doing good.

I installed Cyberpanel on multiple VPS machines.

Every site works find but after few refreshes during development site stop opening and gives error

This site can’t be reached

Check if there is a typo in example.tld.

When I change Internet connection and it works fine on other router but doesn’t open for 1 day around on that previous internet and same thing happens later on on other router as well

I checked Ip address in CSF Firewall and there were no blocks on ip address but site doesn’t open

Kindly help me.
thanks all

where you are managing your DNS the error that you shared is DNS error

DNS are hosted on cyberpanel.