mpris-scrobbler: Service doesn't submit tracks, but manually running `mpris-scrobbler` does (F36, 0.5)

Scrobbling from Spotify behind a proxy has been broken for years and Spotify are unwilling to fix it, so this is a lifesaver.

I don’t mind having it run in a tmux session or something, so not the end of the world, but I’m confused as to why the service doesn’t work. My only thought is it’s something to do with the proxy but I don’t really know how to drill into that – http(s)_proxy is set for both my user and root, and in GNOME config.

Output of systemctl --user status mpris-scrobbler.service (last.fm does not receive anything):

 ~/l/mpris-scrobbler    systemctl --user status mpris-scrobbler.service                                                                                                                 16.3s  Tue 17 May 2022 17:08:08 BST
● mpris-scrobbler.service - daemon to scrobble tracks loaded from the MPRIS DBus interface to compatible services
     Loaded: loaded (/usr/lib/systemd/user/mpris-scrobbler.service; enabled; vendor preset: disabled)
     Active: active (running) since Tue 2022-05-17 17:06:36 BST; 1min 43s ago
       Docs: man:mpris-scrobbler
   Main PID: 34790 (mpris-scrobbler)
      Tasks: 1 (limit: 38369)
     Memory: 2.7M
        CPU: 12ms
     CGroup: /user.slice/user-1000.slice/user@1000.service/app.slice/mpris-scrobbler.service
             └─34790 /usr/bin/mpris-scrobbler -vv

May 17 17:08:14 rd015816 mpris-scrobbler[34790]: DEBUG   changed::volume:               no
May 17 17:08:14 rd015816 mpris-scrobbler[34790]: DEBUG   changed::position:            yes
May 17 17:08:14 rd015816 mpris-scrobbler[34790]: DEBUG   changed::playback_status:      no
May 17 17:08:14 rd015816 mpris-scrobbler[34790]: DEBUG   changed::track:               yes
May 17 17:08:14 rd015816 mpris-scrobbler[34790]: DEBUG   events::add_event:now_playing[Spotify] in 0.000s, ellapsed 0.000s
May 17 17:08:14 rd015816 mpris-scrobbler[34790]: DEBUG   events::add_event:queue[Spotify] in 131.000 seconds
May 17 17:08:14 rd015816 mpris-scrobbler[34790]: DEBUG   events::triggered(0x7ffc819c8a90:0x7ffc819c8a98):now_playing
May 17 17:08:14 rd015816 mpris-scrobbler[34790]: INFO    scrobbler::now_playing[Spotify]: True Lovers//Holy Holy//Paint
May 17 17:08:14 rd015816 mpris-scrobbler[34790]: WARNING curl::multi_timer_activation:failed: API function called from within callback
May 17 17:08:14 rd015816 mpris-scrobbler[34790]: DEBUG   events::add_event:now_playing[Spotify] in 65.000s, ellapsed 0.000s

Result of starting the scrobbler manually:

~/l/mpris-scrobbler    mpris-scrobbler -v                                                                                                                                                      Tue 17 May 2022 17:08:20 BST
INFO    scrobbler::now_playing[Spotify]: True Lovers//Holy Holy//Paint
INFO     api::submitted_to[last.fm]: ok
^[[A^[[BINFO    scrobbler::now_playing[Spotify]: True Lovers//Holy Holy//Paint
INFO     api::submitted_to[last.fm]: ok
INFO    scrobbler::scrobble:(   0) True Lovers//Holy Holy//Paint
INFO     api::submitted_to[last.fm]: ok
INFO    scrobbler::now_playing[Spotify]: True Lovers//Holy Holy//Paint
INFO     api::submitted_to[last.fm]: ok

I feel like this is highly likely to be user error, but I can’t for the life of me figure out what I’ve done wrong. Any help would be appreciated, thanks.