Hello,
A bug that's been around for over a year (Just getting around to posting), it's been around since whatever version first introduced multiple profiles.
First, there seems to be a big difference between "Use <profilename> for all URLs" for any default profile and "Use Proxy default for all URLs" under the default profile with the default pointing to the custom profile, the latter works as indicated but the former does not... most of the time (sometimes both work equally but not always)
Secondly, this seems to regularly occur immediately after an update is pushed. After the new version is installed, FoxyProxy can't find the proxy.
The setup:
Using FoxyProxy as a local SOCKS proxy pointing to localhost:1080 running Android SDK adb.exe forwarding to a tethered Android phone.
Works great otherwise!