But one test you can do is try opening a page manually to see if the splash page loads.
Block
Applies the following settings to a client:
Firewall rule applied to block all communication with other devices on the Network (only applies to traffic that traverses the Cisco Meraki device that has the block is configured)
Blocked Splash Page will be displayed when user tries to load a web page
I am not a Cisco Meraki employee. My suggestions are based on documentation of Meraki best practices and day-to-day experience.
Please, if this post was useful, leave your kudos and mark it as solved.