On attempting to renew the APNs for MDM certificate, you see the error message:
Uploaded certificate mismatches with the AW certificate request
This error if the .plist uploaded into the AirWatch Console during the APNs renewal process was created from a different browser session. The console is expecting a certificate that was renewed using a CSR file generate within the same browser session. To resolve, open the AirWatch Console and the Apple Push Certificate Portal in separate tabs, and complete the renewal process without closing either tab.