Ted here from Shopify, thanks for reaching out to us!
I've taken a look at your store and can confirm that your account is active and nothing has been disabled. I was also able to access the checkout with no issues, as shown here for example. You should also see an abandoned cart within your admin shortly, which also confirms that your checkout is accessible.
Regardless though, going by the screenshot; this is a browser or internet error that's appearing and not a Shopify error notification. I'd recommend updating your browser and clearing your cached files on Chrome, then trying to access the checkout again. If you are still able to replicate it, could you please try a different device and internet connection instead? For example, can you access the checkout using your mobile phone and mobile phone provider? Has this occurred for many customers?
Please let me know how this goes!
All the best,
I have a similar issue happening where some of my customers can't access the checkout page on Chrome Browser. Shopify support is not being helpful at all. If they are able to access my store but not the checkout page, it's definitely an error from Shopify checkout server.
Did you got your thank you page fixed?