org.springframework.web.client.ResourceAccessException: I/O error on GET request for 'https://[myendpoint]'

PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target;

I am working on a REST call from my windows development machine.

I have tried following the guidelines for adding a certificate in my java keystore in:"C:\Program Files (x86)\Java\jre1.8.0_271\lib\security\cacerts"

Infact I have another JAVA directory in:C:\Program Files\Java\jre1.8.0_271\lib\security\cacerts

I have tried storing my certificate in both keystores.

At the site, that is exposing a rest service, I save the certificate from my Google Chrome webbrowser

...and under the details tab clicking on the "Copy to file" button.I use the Certificate Export Wizard and pick the first "DER encoded binary x.509 (.CER)" option.

I give the certificate a name "mycert.cer". Once I have it exported, I use the keytool command and add it to my JAVA keystore with the following command:

keytool -import -noprompt -trustcacerts -alias mycert -file "d:\MyCertificates\mycert.cer" -keystore "C:\Program Files (x86)\Java\jre1.8.0_271\lib\security\cacerts" -storepass changeit

I get a confirmation, that it is stored.

I try to invoke my a rest call and I get the same error. Can someone please clarify, what I need to do more? What am I missing?

I am doing all this in admin mode (local adminstrator) on my developer machine.