I know this is an old thread, but let me confirm this for the benefit of others.
1560 APs are not supported for Mesh on the 8.3 code train. It is mentioned under the heading 'Key Features Not supported on Cisco Aironet 1560...' https://www.cisco.com/c/en/us/td/docs/wireless/controller/release/notes/crn83mr1.html#concept_FF724317C5244CC6A6D75C27BCDBC600
You can upgrade to a stable code on 8.5 or 8.8 where this support has been provided. The release notes for 22.214.171.124 mentions that support for Mesh has been added for 1560 APs - https://www.cisco.com/c/en/us/td/docs/wireless/controller/release/notes/crn84.html#ap-wave2
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