The firmware need to be the same for the 535s and 515s to cluster together. You will need to manually upgrade one of the 535s and add it to the cluster. Once it is joined, the remaining can join, download the firmware from the first 535, and upgrade themselves. They will then reboot and join the 515 cluster.
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Dustin Burns
Lead Mobility Engineer @Worldcom Exchange, Inc.
ACCX 1271| ACMX 509| ACSP | ACDA | MVP Guru 2022
If my post was useful accept solution and/or give kudos
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