Hi @geopr,
Your code might be pointing to certificates from another project whose certificate would have been expired. Please create a new key store with the credentials from the below project and also use the Basic Auth user name / password from the below project on your code and retry.
I also faced the same issue. When I debugged the java code, it happened in the step of validating the server's certificate. Note that during SSL handshaking, client will first validate Server's certificate, then server will validate client's certificate.
The problem is caused by my company's proxy setting. The problem disappears on my other laptop. Therefore, you could solve the issue by adding proxy to java http client.