in the last days i saw this sometimes, now its permanent. internet connection is good, same on all browsers / mobil, vpn is off, no proxis, cache is flushed, coockies deleted. i change the index.html to a very basic test page. domain provider says every thing is fine from their site, except:
Per my check, your domain pointed to Custom nameservers. In this case you need to contact your DNS Provider, as, per my check, their IP for your domain is not resolved.