Why is my online store not loading on multiple browsers?

I had 2 potential new business suppliers tell me that they can’t get my Shopify website to load today. Both never visited it before, both tried multiple devices/browsers. Same error message on homepage, and when trying to click through via Google search and shopping ads. No problem with DNS settings according to host. Many others are able to access it no problem, including Shopify’s tech support people and everyone in our business, but how many customers are unable to load our page? How much business are we losing if x% of new users never get to visit our site and have no other contact info for us? It appears this is not an isolated issue, what are Shopify not telling us?