Error 520 client side

I am having trouble finding out the cause of this problem since I am not able to replicate it, majority of the devices and different internet connections I use have no problem loading my website, but I received a report where a single client was having problems loading the homepage itself, upon checking there have been 74 reports of error 520 in error analysis of cloudflare. The client themselves have already come into contact with their internet provider and said that it was not a problem on their side as it was a server problem with host. I have suggested using mobile data with the same device of the client to see if the website would load and it did.

I am leaning towards the problem being with their internet configuration as I have checked with our hosting provider and there were no problems detected and the client is the only report I have received having this problem, or could this be because I only have a free account in cloudflare?

I have asked the client to run a tracert and send the har file when the loading error occurs. In regards to the tracert it completed its route and doesn’t seem to have a problem, and in the har file I am not sure how to move forward with this information, assuming that this file would be of help in this thread I asked for it.

Any insight would be really helpful and I would appreciate it thanks!
sidenote: I am not familiar with the standard of how to report such issues so bare with me :sweat_smile:

Mobile data success suggests it’s isolated to their hardwired ISP. Do you know which datacenter they’re going through? will show the Colo. name.

And if you haven’t seen this, here it is:

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Hello thanks for replying, what I did was pause cloudflare and that single client was able to access which further indicates that the problem was indeed with their isp but I am not well versed enough in networking to pursue that matter further thats why i resulted in asking for help here and appreciate the community, also I cannot afford to pause cloudflare that’s why this is not a permanent solution.

And yes i have seen the document you linked:
[Quick Fix Ideas]
1)I have no firewall rules placed and load balancer is not enabled.
2)I have ruled this out as it seems that 200-300 of my clients are able to access at the same time and this one client is the only one experiencing it.
3)The client have already come into contact with their hosting provider and stated that they have no problems on their side and insisted that it was on the hosting server.(I have ruled out the cause to be my hosting provider as I have stated the client was able to access the website when I paused the cloudflare)
4)My header file is only 4.3kb.
5)Always Online has always been disabled
6)I have submitted a ticket but as of today no response yet and yes I have upgraded to professional to get a better chance for them to respond to this ticket.

In regarding to the datacenter they are going through which I also had initially thought was the root of the problem resulted in operational upon checking their status here cloudflare status, their colo was NRT.

Summary: pausing cloudflare allowed the client to access the website without resulting into a 520 error, datacenter of cloudflare was operation, mobile data works but not their wifi, I believe their internet connection is the prime suspect as they are greeted with a 520 error in every device whether it be desktop or mobile.

Am I right to think that after troubleshooting the possible problems and narrowing it down to what I am able to do, that the best way for this to be resolved would be for cloudflare themselves to check the rayid and what happened with the connection and who blocked who whether it was client who blocked cloudflare or cloudflare to client due to some configurations that the client may have.

Thank you again for replying! I am liking how I am able to learn new things while troubuleshooting. Have a nice day and sorry for the late reply.

Open a ticket (instructions below) and provide as many Ray IDs as you can for those 520 errors. And let them know the ISP. They may provide further instructions on how to troubleshoot.

To contact Cloudflare Customer Support, login & go to and select get more help. If you receive an automatic response that does not help you, please reply and indicate you need more help.

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Yes I have done that when I first submitted this topic, unfortunately they are not responsive but I made that ticket when my account was still free, I’ll try to resubmit a new ticket since I have upgraded my account; maybe they will pay more attention to it.

As of writing this moment the problem has been resolved and it was done by the client’s internet service provider, the client was not able to provide details sadly, all we know is the client urged their isp to do something about it.

In regards to the details of the support ticket, before we could go any further the client resolved it with their isp. The information that cloudflare provided was:

I can confirm then when I use our internal tools to test accessing your site with the IP address of ***.**.***.** , I am indeed presented with a 520 error, even from different colos, which is unusual that this is the only IP that triggers this error (I tested with a few more).

Note: I have censored the client’s ip address.

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