A 404 Not Found error could occur for a variety of reasons. In the context of Ory Oathkeeper, it could be due to a misconfiguration in the access rules or the absence of a matching rule for the incoming request. Ory Oathkeeper uses a decision engine to authorize HTTP requests. The first step in this process is Access Rule Matching, which verifies that the HTTP method, path, scheme, and host of the incoming HTTP request conform to your access rules. If no access rules match, the request is denied and a 404 error could be returned ([source](https://www.ory.sh/docs/oathkeeper#decision-engine)). In the case of a configured rule, ensure that the rule correctly matches the incoming request. The rule should correctly define the HTTP method, the URL, and other parameters of the incoming request. If the rule is not correctly configured, Ory Oathkeeper may not be able to match the incoming request to the rule, resulting in a 404 error. Here is an example of a rule configuration:

json {    "id": "some-id",    "upstream": {    "url": "<http://my-backend-service>",    "preserve_host": true,    "strip_path": "/api/v1"    },    "match": {    "url": "<http://my-app/some-route/<.*>>",    "methods": ["GET", "POST"]    },    "authenticators": [{ "handler": "anonymous", "config": { "subject": "anon" } }],    "authorizer": { "handler": "allow" },    "mutators": [{ "handler": "noop" }]   }

([source](https://www.ory.sh/docs/oathkeeper/api-access-rules#handler-configuration)) If the rule is correctly configured and the error persists, it could be due to other issues such as network problems or issues with the upstream server.