In fact the only differrence that I see from a working one and a non working one are :
WORKING
root@SheBe:~# analyseplugin lp4pole_1671.so
Plugin Name: "4 Pole Low-Pass Filter with Resonance (FCRCIA)"
Plugin Label: "lp4pole_fcrcia_oa"
Plugin Unique ID: 1672
Copyright: "GPL"
Must Run Real-Time: No
Has activate() Function: Yes
Has deactivate() Function: No
Has run_adding() Function: No
Environment: Normal or Hard Real-Time
Ports: "Cutoff Frequency" input, control, 2.08333e-05*srate to 0.5*srate, default 0.5*srate, logarithmic
"Resonance" input, control, 0 to 4, default 0
"Input" input, audio
"Output" output, audio
NOT WORKING
root@SheBe:~# analyseplugin tap_tubewarmth.so
Plugin Name: "TAP TubeWarmth"
Plugin Label: "tap_tubewarmth"
Plugin Unique ID: 2158
Maker: "Tom Szilagyi"
Copyright: "GPL"
Must Run Real-Time: No
Has activate() Function: No
Has deactivate() Function: No
Has run_adding() Function: Yes
Environment: Normal or Hard Real-Time
Ports: "Drive" input, control, 0.1 to 10, default 2.575
"Tape--Tube Blend" input, control, -10 to 10, default 10
"Input" input, audio
"Output" output, audio
NOT WORKING
root@SheBe:~# analyseplugin harmonic_gen_1220.so
Plugin Name: "Harmonic generator"
Plugin Label: "harmonicGen"
Plugin Unique ID: 1220
Copyright: "GPL"
Must Run Real-Time: No
Has activate() Function: Yes
Has deactivate() Function: No
Has run_adding() Function: Yes
Environment: Normal or Hard Real-Time
Ports: "Fundamental magnitude" input, control, -1 to 1, default 1
"2nd harmonic magnitude" input, control, -1 to 1, default 0
"3rd harmonic magnitude" input, control, -1 to 1, default 0
"4th harmonic magnitude" input, control, -1 to 1, default 0
"5th harmonic magnitude" input, control, -1 to 1, default 0
"6th harmonic magnitude" input, control, -1 to 1, default 0
"7th harmonic magnitude" input, control, -1 to 1, default 0
"8th harmonic magnitude" input, control, -1 to 1, default 0
"9th harmonic magnitude" input, control, -1 to 1, default 0
"10th harmonic magnitude" input, control, -1 to 1, default 0
"Input" input, audio, -1 to 1
"Output" output, audio, -1 to 1