Site cannot be reached when NextDNS is enabled

I have recently setup my own website using CNAME. I visited the site once and got this error page. Then after setting it up correctly, NextDNS cannot pick it up and thows the same "This site can't be reached" error. 

When I disable NextDNS, it works. So I just want to know how to clear the DNS Cache for NextDNS. Note that I have cleared the brower & device. It works well without NextDNS.

Only NextDNS have this problem and only for this website. Need to know the trick to re-enable the website as usual.