Site Periodically Inaccessible by Customer and Myself

[Zigmo]

NOTE: The Forum will not take the full post. I had to reply 5 times to include all the details. 

A few weeks ago I was working on my site and out of the blue my browser started throwing a 403 error when I tried to access my site.  I tried several browsers and links.  I was able to access other sites including other shopify sites just fine.  I tried on my phone which was on WiFi and the same issue.  I turned off Wifi and it started working on my phone.   Lucky I have two ISP and when I switch my computer to the other WiFi network it worked fine too. Is this the ISP flagging my site?  

[Zigmo]

I contacted Shopify and they did not get an error when trying to access my site. They said something about my DNS setting on the domain looked wrong and they thought that might be the issue.  That sounded odd since my site has been working for years.  I checked the DNS settings and they were already set to what they told me to set them.  I blew it off as an anomaly because after about 12 hours I switched back to the original ISP and the site work again.  Strange.

[Zigmo]

Fast forward to yesterday and I received a Facebook message from a customer saying they were unable to access my site on both thier phone and desktop.  I asked them if thier phone was using the same wifi as the desktop and it was.  I had them use thier cellular data and he was able to get to my site. This really sounds like something in my site or Shopify is tripping alerts at ISPs.

[Zigmo]

Customer got this Error:

You don't have permission to access / on this server. Additionally, a 403 Forbidden error was encountered while trying to use an ErrorDocument to handle the request.

[Zigmo]

This morning I too am getting errors when accessing my site:

Chrome Error:

Your connection is not private

Attackers might be trying to steal your information from threadstax.com (for example, passwords, messages, or credit cards).

NET::ERR_CERT_COMMON_NAME_INVALID

Automatically send some system information and page content to Google to help detect dangerous apps and sites. Privacy policy

ReloadHIDE ADVANCED

threadstax.com normally uses encryption to protect your information. When Google Chrome tried to connect to threadstax.com this time, the website sent back unusual and incorrect credentials. This may happen when an attacker is trying to pretend to be threadstax.com, or a Wi-Fi sign-in screen has interrupted the connection. Your information is still secure because Google Chrome stopped the connection before any data was exchanged.

You cannot visit threadstax.com right now because the website uses HSTS. Network errors and attacks are usually temporary, so this page will probably work later. Learn more.

Internet Explorer Error:

This site is not secure

This might mean that someone’s trying to fool you or steal any info you send to the server. You should close this site immediately.

The hostname in the website’s security certificate differs from the website you are trying to visit.

Error Code: DLG_FLAGS_SEC_CERT_CN_INVALID

Because this site uses HTTP Strict Transport Security, you can’t continue to this site at this time.

[Zigmo]

Just received the following comment from a customer.  This has to be fixed.  Going to contact support again.  

[Bezeus]

Please how did you resolve this?

[GoldFreeze]

I have the same problem that you had. I would like to know how you fixed it. 

this was the error:

Your connection is not private

Attackers might be trying to steal your information from threadstax.com (for example, passwords, messages, or credit cards).

NET::ERR_CERT_COMMON_NAME_INVALID

[somersetfoodie]

Can anyone offer a solution here? Our Shopify site is blocked on some WiFi channels all over the Uk at the moment. But if you use 4G you can see it.

somersetfoodie.com

What can I do to fix this?