You need to upgrade your ZD to a newer version of code to work with R550. You have a couple of choices:
- Version 10.4.1 - which specifically adds support for R550 (10.4 did not have support).
- Version 10.5 - which has native support for R550.
Please note, you will need to upgrade to 10.2.x prior to upgrading to 10.4.1. However 10.5.1 supports a direct upgrade from your version. Both of the above versions also support your existing R320 APs.
Please ensure you read each version's release notes carefully and you backup your controller config prior to each upgrade.
I hope that helps,