After upgrading the cloud enabled management gateway server from 7.5 to 7.6 the logs on the gateway show numerous errors.
Client 192.169.1.16: Certificate Verification: Error (20): unable to get local issuer certificate (proto:TLSv1; certCN:/CN=CL-W7-01.epm.com; serial:76EF39DD1307B4BF31EBB96F02E1A2A30994A5E4; issuer:/CN=SMP SMP-W2K8-01.epm.com Agen)
Certficate and hash information on the gateway was not updated.
Delete the SMP server and site servers from the list of servers in the gateway and add them back in.