The problem is this:
On the Meraki side, let's say you have 5 (this can be any number greater than 1) firewalls.
In Meraki speak, if all 5 are in the same "organization", S2S is a few clicks & AutoVPN takes over. No pre-shared secret, no keys.
You turn on VPN, say yes to whatever subnets you want in the vpn & save.
On the ER side, I have to create 5 peers to connect to the Meraki side.
Meraki will only expose one connection for a 3rd party S2S & therein lies the problem.
Not all the tunnels connect & there's no good way to fix it.