Prepare join failed. Got HTTP status 500 from REST call post to http://172.23.97.56:8091/engageCluster2

• 2 node cluster

rebalance params :

1. Disable autofailover -
settings/autoFailover params : timeout=120&enabled=false&failoverOnDataDiskIssues%5Benabled%5D=false&maxCount=1&failoverServerGroup=false

2. Enabled n2n on:
[2021-03-13 06:02:28,957] - [remote_util:4676] INFO - command to run: /opt/couchbase/bin/couchbase-cli node-to-node-encryption -c http://localhost -u Administrator -p password --enable
[2021-03-13 06:02:29,300] - [ntonencryptionBase:58] INFO - Output of node-to-node-encryption command is ['Turned on encryption for node: http://172.23.97.52:8091', 'Turned on encryption for node: http://172.23.97.53:8091', 'SUCCESS: Switched node-to-node encryption on']

3. Enable encryption level to control
[2021-03-13 06:02:30,135] - [remote_util:4676] INFO - command to run: /opt/couchbase/bin/couchbase-cli setting-security -c http://localhost -u Administrator -p password --set --cluster-encryption-level control
[2021-03-13 06:02:30,346] - [ntonencryptionBase:95] INFO - Output of setting-security command is ['SUCCESS: Security settings updated']

4. adding remote node @172.23.97.56:8091 to this cluster @172.23.97.52:8091

5. Rebalance fails:

[2021-03-13 06:03:22,530] - [rest_client:1018] ERROR - POST http://172.23.97.52:8091/controller/addNode body: hostname=http%3A%2F%2F172.23.97.56%3A8091&user=Administrator&password=password&services=kv headers: {'Content-Type': 'application/x-www-form-urlencoded', 'Authorization': 'Basic QWRtaW5pc3RyYXRvcjpwYXNzd29yZA==', 'Accept': '*/*'} error: 400 reason: unknown b'["Prepare join failed. Got HTTP status 500 from REST call post to http://172.23.97.56:8091/engageCluster2. Body was: \\"[\\\\\\"Unexpected server error, request logged.\\\\\\"]\\""]' auth: Administrator:password

Not seen with - 7.0.0-4617