Following recent updates to 7.4 (return to mysql) and change to test.squeezenetwork.com, Last.fm Radio is no longer working.  Scrobbling works fine.

Last.fm accounts are shown in the My Apps section of test.squeezenetwork.com but there is no "authorise this account" button.

When attempting to play via SC, the account credentials are recognised (and stations like Recommended or Loved are shown as options in the web interface) but stations will not play.  Error message "Problem: cannot connect to server for lfm:..." is shown at the bottom of the web interface.

SC log shows:

[09-08-18 16:23:39.4189] Slim::Plugin::LastFM::ProtocolHandler::getNextTrack (134) Getting next track from SqueezeNetwork (http://www.test.squeezenetwork.com/api/lastfm/v1/playback/getNextTrack?station=user%2FSiduhe%2Frecommended&isScrobbling=1&discovery=0&account=Siduhe)
[09-08-18 16:23:39.9405] Slim::Plugin::LastFM::ProtocolHandler::_gotNextTrack (157) Got Last.fm track: { error => undef }
[09-08-18 16:23:39.9428] Slim::Plugin::LastFM::ProtocolHandler::new (33) Remote streaming Last.fm track: 
[09-08-18 16:23:39.9433] Slim::Player::Song::open (456) Warning: stream failed to open [lfm://user/Siduhe/recommended].
[09-08-18 16:23:39.9462] Slim::Plugin::LastFM::ProtocolHandler::getNextTrack (134) Getting next track from SqueezeNetwork (http://www.test.squeezenetwork.com/api/lastfm/v1/playback/getNextTrack?station=user%2FSiduhe%2Frecommended&isScrobbling=1&discovery=0&account=Siduhe)
[09-08-18 16:23:40.3466] Slim::Plugin::LastFM::ProtocolHandler::_gotNextTrack (157) Got Last.fm track: { error => undef }
[09-08-18 16:23:40.3488] Slim::Plugin::LastFM::ProtocolHandler::new (33) Remote streaming Last.fm track: 
[09-08-18 16:23:40.3493] Slim::Player::Song::open (456) Warning: stream failed to open [lfm://user/Siduhe/recommended].

When connecting a player directly to SN and trying to play Last.fm, I get "
Current player:
Home  /  Last.fm Error
Your player is not authorized to use mysqueezebox.com." 

My player does show as a connected player in SN and will play internet radio streams quite happily.

All testing done with a Squeezebox 3 running SqueezeboxServer-7.4-28194.exe