Hi@ehsan230564
"SPARE is unreachable" means the secondary device is not reaching the Meraki Cloud with the "Physical IP".
Could you please re-check the IP Addresses configured on the Secondary MX and internet access is allowed for the same?
How about this?
Delete the primary device from the network and check if your spare is coming live?
Regards,
Ajit
AjitsNW@gmail.com
www.ajit.network