OpenDistro 1.1.0 S3 plugin not working

Hello, I am having some issues with S3 plugin.

I am using OpenDistro 1.1.0 OSS
elasticsearch-oss-7.1.1-amd64.deb
repository-s3-7.1.1.zip

openjdk version “11.0.3” 2019-04-16
OpenJDK Runtime Environment (build 11.0.3+7-Ubuntu-1ubuntu218.04.1)
OpenJDK 64-Bit Server VM (build 11.0.3+7-Ubuntu-1ubuntu218.04.1, mixed mode, sharing)

bin/elasticsearch-keystore add s3.client.my_s3.access_key
bin/elasticsearch-keystore add s3.client.my_s3.secret_key

POST _nodes/reload_secure_settings

or ES restart…

PUT _snapshot/my_s3
{
“type” : “s3”,
“settings” : {
“bucket” : “test”,
“client” : “my_s3”,
“endpoint” : “https://blablabla.com
}
}

I am getting this reply

{
“error”: {
“root_cause”: [
{
“type”: “repository_verification_exception”,
“reason”: “[my_s3] path is not accessible on master node”
}
],
“type”: “repository_verification_exception”,
“reason”: “[my_s3] path is not accessible on master node”,
“caused_by”: {
“type”: “i_o_exception”,
“reason”: “Unable to upload object [tests-pWykBUqcT9SUX8gWoPWeng/master.dat] using a single upload”,
“caused_by”: {
“type”: “sdk_client_exception”,
“reason”: “Unable to execute HTTP request: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target”,
“caused_by”: {
“type”: “s_s_l_handshake_exception”,
“reason”: “PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target”,
“caused_by”: {
“type”: “validator_exception”,
“reason”: “PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target”,
“caused_by”: {
“type”: “sun_cert_path_builder_exception”,
“reason”: “unable to find valid certification path to requested target”
}
}
}
}
}
},
“status”: 500

Could you please give me some advice?

Many thanks.