Authentication type is ApiKey.
Version: 7.14.1
When rule is already Enabled, there is no trouble calling the API endpoint for _enable. Returns Status Code 204.
But if rule is actually Disabled (and therefore need to Enable), an error occurs when attempting _enable action. Can call hit the _disable endpoint using same Header with same ApiKey value, the only material change is using the /_enable endpoint versus the /_disable one. (/_mute_all and /unmute_all both work as expected).
POST https://{kibana host}:5601/api/alerting/rule/{rule id}/_enable with 0-byte payload
Response...
{"statusCode":400,"error":"Bad Request","message":"Error enabling rule: could not create API key - Unsupported scheme \"ApiKey\" for granting API Key"}