Did you ever get this working CarOneAdmin??
We are having same issues, but with Win 10 and Win 7 laptops.
Setup new SSID using 802.1x and meraki authentication. Mobile devices connect fine, but Win10 and Win7 laptops either say connecting...... for ages or come up with Certificate related issues same as those you posted.
Win7 machine fully updated as is Win 10 machine.
We want to be able to setup two Wifi SSIDS, internal and guest. Internal we'd like only those devices registered in Meraki MDM to be able to access, don't want to have to type userid or passwords etc, Just basically, if registered in MDM, then devices is allowed to connect to the Wifi SSID, not registered, no connection.
As said, this does work for Mobile (IPhones tested currently) but not on laptops.
Any help appreciated
cheers
Gary