It appears that when using a URL Base setting within Sonarr\Radarr, Requestrr has issues following the redirect that's returned for POSTs. It appears to be switching to a GET request which also no longer includes the API Key. For example below, a URL Base of /sonarr is configured for use behind a reverse proxy.
POST /api/v3/series HTTP/1.1
Host: sonarr_v3:8989
Content-Type: application/json
X-Api-Key: **snip**
Content-Length: 415
{"title":"Outsiders","qualityProfileId":6,"profileId":6,"languageProfileId":1,"titleSlug":"outsiders","monitored":true,"images":[],"tvdbId":303236,"tags":[],"seriesType":"standard","year":2016,"seasonFolder":true,"rootFolderPath":"/tv","id":null,"seasons":[{"seasonNumber":0,"monitored":false},{"seasonNumber":1,"monitored":true},{"seasonNumber":2,"monitored":false}],"addOptions":{"searchForMissingEpisodes":true}}
HTTP/1.1 303 See Other
X-Application-Version: 3.0.3.717
Location: /sonarr/api/v3/series
X-ApplicationVersion: 3.0.3.717
Cache-Control: no-cache, no-store, must-revalidate, max-age=0
Pragma: no-cache
Expires: 0
Access-Control-Allow-Origin: *
Content-Type: text/html
Server: Mono-HTTPAPI/1.0
Date: Sun, 15 Mar 2020 21:38:27 GMT
Content-Length: 0
Keep-Alive: timeout=15,max=78
GET /sonarr/api/v3/series HTTP/1.1
Host: sonarr_v3:8989
HTTP/1.1 401 Unauthorized
X-Application-Version: 3.0.3.717
Cache-Control: no-cache, no-store, must-revalidate, max-age=0
Pragma: no-cache
Expires: 0
Content-Type: application/json; charset=utf-8
Server: Mono-HTTPAPI/1.0
Date: Sun, 15 Mar 2020 21:38:27 GMT
Transfer-Encoding: chunked
Keep-Alive: timeout=15,max=77
1d
{
"error": "Unauthorized"
}
0
This shows up in Sonarr as the the following error due to the GET request with no API key: