Failed to set up new Pathfinder Server: SSO Login Issues

[SuperSixOne]

Apparently CCP has iterated on the character endpoint recently and released v5 while simultaneously deprecating the v4 character endpoints. This is causing an issue for us setting up a new pathfinder instance, as on attempting to login we get:

Access Denied - No characterData could be loaded.

I found the error in the ESI logs:

{ "message": "GET /v4/characters/675835178/?datasource=tranquility HTTP/1.1 → 404 Not Found 21", "context": { "data": { "response": { "code": 404, "phrase": "Not Found", "version": "1.1", "res_header_content-length": "21", "error_msg": "Not found" }, "cache": { "status": "MISS" }, "request": { "method": "GET", "url": "https://esi.evetech.net/v4/characters/675835178/?datasource=tranquility", "host": "esi.evetech.net", "path": "/v4/characters/675835178/", "target": "/v4/characters/675835178/?datasource=tranquility", "version": "1.1" }, "stats": { "time": "0.38366" } }, "tag": "warning" }, "level": 400, "level_name": "ERROR", "channel": "api_esi_requests", "datetime": "2022-04-04T05:33:35.920659+00:00", "extra": { "path": "/sso/callbackAuthorization", "ip": "192.168.1.1" } }

Switching V4 -> V5 allows me to return data.