There is a guide on Okta site, how to develop the connector. You may want to start from there - https://help.okta.com/en/prod/Content/Topics/Provisioning/opp/OPP-build-SCIM-using-SDK.htm
Have you implemented a method which returns “provisioning capabilities” supported by your connector? It seems to me from the log, that it’s not properly implemented, hence the exception.