Flex Gateway: Agent Registry of type RR returned HTTP status code 400 and payload Failed to create target

This error occurs during the self-managed Flex Gateway registration process. It indicates that an attempt was made to register a Flex Gateway with a name that is already in use by an active Flex Gateway within the same organization and environment. Flex Gateway names must be unique across your Anypoint organization, regardless of whether the gateway is operating in Local Mode or Connected Mode.

Error:

$ docker run --entrypoint flexctl -u $UID \
  -v "$(pwd)":/registration mulesoft/flex-gateway \
  registration create --organization=09a1051d-88re-trac-ted-12345cb49 \
  --token=536cdb72-5a31-4574-r3tr4-ct3d24-57c4c7a \
  --output-directory=/registration \
  --connected=true \
  ak-fgw-docker-connected
Starting registration, please be patient.
Error: invalid response: HTTP/1.1 400 Bad Request
Transfer-Encoding: chunked
Cache-Control: no-cache, no-store, max-age=0, must-revalidate
docker run --rm \
Connection: keep-alive
Content-Type: application/json
Date: Sun, 15 Jun 2025 18:23:06 GMT
Expires: 0
Pragma: no-cache
Server: nginx
Strict-Transport-Security: max-age=31536000; includeSubDomains
X-Anypnt-Trx-Id: f3167
X-Content-Type-Options: nosniff
X-Frame-Options: DENY
X-Xss-Protection: 0

143
{"message":"Agent Registry of type RR returned HTTP status code 400 and payload Failed to create target ak-fgw-docker-connected, organizationId 09a1051d-88re-trac-ted-12345cb49, environmentId efd2ece5-0000-0000-re-trac-ted-12345c9, an active target with the same name already exists in this organization and environment"}
0

​​Root Cause:

The most common cause is attempting to register a new Flex Gateway instance with a name that is already assigned to an existing, active Flex Gateway registration in your Anypoint Organization.