Is that a Layer 7 policy on the Firewall rules, or a Content Filtering policy?
What happens if you whitelist a client and try and access it from that client?
Try removing the rule temporarily and see if you can access the site.
If it’s a Content Filtering rule then Meraki uses Bright Cloud for their URL categories, go to https://www.brightcloud.com and put the URL in the lookup on that page to see how it’s being classified.