If you encounter the above error, you should first check if the edge node or other JPD instance that you are trying to set up access federation with has the same "Base URL" (which you can check in the UI under Admin -> General Settings) as the main instance. If so, please change the base URL. If you are using the same base URL across instances due to a use case involving geo-load balancing and docker requests, you can override the base URL in a reverse proxy with the X-JFrog-Override-Base-URL header.
After changing the base URL, remove and re-add the edge node or JPD instance with a unique URL. Also, you should confirm in the main instance's $JFROG_HOME/var/etc/access/access.config.yml if the "outbound" section has a URL that is identical to the main instance. If so, change the URL, rename the file to access.config.import.yml, and restart Artifactory.
If the issue still persists, create a ticket with Jfrog support describing the issue, and send over the output of the below queries from the Mission Control DB:
select * from jfmc_server.custom_jpd_url;
select * from jfmc_server.jpd;
select * from jfmc_server.service;