docs: add base URL info to FAQ (#1179)

* Update faq.md

Co-authored-by: TheCatLady <52870424+TheCatLady@users.noreply.github.com>

docs/support/faq.md

@@ -90,6 +90,10 @@ You can also perform the following to verify the media item has a GUID Overseerr
 
 **A:** See "[Some media is missing from Overseerr that I know is in Plex!](./faq.md#some-media-is-missing-from-overseerr-that-i-know-is-in-plex)" for troubleshooting steps.
 
+### Approved series requests keep failing!
+
+**A:** If you configured a base URL in Sonarr, make sure you have set the base URL option appropriately in Overseerr. Also, check that you are using Sonarr v3 and have configured a default language profile in Overseerr.
+
 ## Notifications
 
 ### I am getting "Username and Password not accepted" when attempting to send email notifications via Gmail!