This 403-Forbidden page seems to be coming from your web server itself, not WordPress (so WordPress’ visibility settings wouldn’t come into play here).
This is likely due to permissions or some ACL (access control list) configuration on your web server.
You mentioned “messing around with the .htaccess file”. But on querying your website, I can see your site’s web server is OpenResty, which is based on Nginx, which doesn’t support Apache’s .htacess (at least support is not built-in, unless you’ve taken the trouble to compile a 3rd-party module supporting this).
Let’s try this: create a new blank PAGE, but make sure it doesn’t contain the word “blog” in the title or slug. Change your POSTS page to this new page (from the current /blog/)… and let’s test to see if you can get your posts to display on this new page. What I’m trying to test here is if the path /blog/ is somehow restricted in your web server configuration.
Standing by for your feedback.
PS: Since (I believe) you’re on Godaddy’s Managed WordPress hosting, this is something that should surely fall under “managed WordPress hosting”, and you may want to get in touch with GoDaddy support to help you with this.
PPS: Also, if you have any security plugin, kindly go over the settings to be sure this is not the culprit. You may even want to temporarily disable it.