My website usually is errored 521 (Web Server down) What need I do?

Hello team Cloudflare,

Recent days, my website usually is errored 521 (webserver down).

My website: Click here

So, I contacted to my hosting provider and they told me they hadn’t found ant error (so strange).

And the Cloudflare sent me an email: http://prntscr.com/optn1b

I had tried their solution but no change.

What need I do?

Hi @caphefinvn, the email you received is from Cloudflare to notify you the origin server was unavailable for at least 5-minutes, this tip gives the background, Community Tip - Email alert, origin unreachable. You can opt out of receiving the alert from the email and the above tip has a links on how to troubleshoot if the 521 becomes/is a persistent issue.

but the 521 error usually occur