Issues with Kubernetes discovery

Hi everyone, I'm facing an issue while trying to discover the Cluster Kubernetes on GCP and AWS clouds.
For instance for GCP I'm getting this discovery log: 

Kubernetes Namespace API call failed or there are no Namespaces in the query. Please verify the configuration data and/or user permissions. , Pattern name: Kubernetes, To Check Pattern Log Press Here

in the Pattern log there is:

Exception occurred while executing operation Kubernetes Get Call. Custom operation Failed to run script due to the following error: JAVASCRIPT_CODE_FAILURE: com.snc.sw.exception.CommandFailureException: Received null response for GET call of URL: https://xx.xxx.xxxx.xxx/api/v1/namespaces?limit=50 .Please check the mid server logs for exact error. Most probable cause is SSL exceptions /certificate exception/ configured URL. (ad_hoc:EvalClosure-get namespaces--986886108; line 17)

or

Exception occurred while executing operation Kubernetes Get Call. Custom operation Failed to run script due to the following error: JAVASCRIPT_CODE_FAILURE: com.snc.sw.exception.CommandFailureException: Received null response for GET call of URL: https://gke-xxxxxxxxxxxxxx.nameofdatacenter.amazonaws.com:port/api/v1/namespaces?limit=50 .Please check the mid server logs for exact error. Most probable cause is SSL exceptions /certificate exception/ configured URL

I can't figure it what am I missing, the MID server associated with the cluster discovery is the right one, there are all the properties configured, we also enabled the role to call specific APIs to the related K8S to have read permissions, both for AWS and GCP.

Thank you