Why is my site blocked by certain ISPs?

[grandsusdesigns]

So we have reached out to support on our issue. We were operating well and then suddenly last week our customers said they were unable to access our site from their home Wifi Networks. I checked our Search console, Domain and Blacklists. When I had our customers use LTE service from their phones it would work. I reached out to Comcast and Spectrum. All I can think is its a certificate issue. I personally use Comcast and have ATT broadband as a backup. In my own home the Wifi isn't blocked. I believe some customers have apps from the ISP as a security feature. Shopify says the TLS or SSl is good. I think its some sort of code but hey if anyone in the community has had this happen before let me know. My site is www.grandsusdesigns.com. 

[StephensWorld]

I can confirm that the site is loading on my end, that your DNS records look good, and that your SSL certificate is active. 

I don't think this would be an issue with the site, but rather your customer's ISP. Unfortunately, I don't think there's anything you can do about this on your end. If the site isn't loading for one or more of your customers, it would most likely be something on their end causing the issue.