Might need to ask a couple more questions here.
Are you pointing the non-meraki VPN tunnel to the Azure public IP address? Are the pre-shared secrets, timeouts, and other configuration options matching what you have setup on Azure?
What happens to the IKE packets outbound from the Meraki MX? Are there any return packets/traffic from the Azure address range?
Azure private LAN IP ----- Azure public <------> Meraki public ----- Meraki private LAN IP range
Are there any rules for port forwarding or 1:1 NAT on the Meraki MX?
Sorry for the million questions, just need to picture a bit more of what actual config is on these respective devices.