When calf audio plugins is installed Gstreamer should recognize it as valid plugins this can be checked by running gst-inspect-1.0 | grep -i calf currently it returns nothing when it should look like this
This seems to be a installation issue according to the developer of pulse effects as seen on #259
This is a large issue due to PulseEffects having a soft dependency for calf (currently not included in the default package for PulseEffects) providing <85% of the software's effects (thus <85% cannot be enabled and is grayed out)
(pulseeffects:25896): pulseeffects-WARNING **: 08:27:42.802: compressor plugin was not found! (pulseeffects:25896): pulseeffects-WARNING **: 08:27:42.802: filter plugin was not found! (pulseeffects:25896): pulseeffects-WARNING **: 08:27:42.802: limiter plugin was not found! (pulseeffects:25896): pulseeffects-WARNING **: 08:27:42.805: bass_enhancer plugin was not found! (pulseeffects:25896): pulseeffects-WARNING **: 08:27:42.805: crossfeed plugin was not found! (pulseeffects:25896): pulseeffects-WARNING **: 08:27:42.805: deesser plugin was not found! (pulseeffects:25896): pulseeffects-WARNING **: 08:27:42.805: exciter plugin was not found! (pulseeffects:25896): pulseeffects-WARNING **: 08:27:42.805: gate plugin was not found! (pulseeffects:25896): pulseeffects-WARNING **: 08:27:42.805: loudness plugin was not found! (pulseeffects:25896): pulseeffects-WARNING **: 08:27:42.805: multiband_compressor plugin was not found! (pulseeffects:25896): pulseeffects-WARNING **: 08:27:42.805: multiband_gate plugin was not found! (pulseeffects:25896): pulseeffects-WARNING **: 08:27:42.805: reverb plugin was not found! (pulseeffects:25896): pulseeffects-WARNING **: 08:27:42.805: stereo_tools plugin was not found! (pulseeffects:25896): pulseeffects-WARNING **: 08:27:42.806: convolver plugin was not found! (pulseeffects:25896): pulseeffects-WARNING **: 08:27:42.814: compressor plugin was not found! (pulseeffects:25896): pulseeffects-WARNING **: 08:27:42.814: filter plugin was not found! (pulseeffects:25896): pulseeffects-WARNING **: 08:27:42.814: limiter plugin was not found! (pulseeffects:25896): pulseeffects-WARNING **: 08:27:42.817: deesser plugin was not found! (pulseeffects:25896): pulseeffects-WARNING **: 08:27:42.817: gate plugin was not found! (pulseeffects:25896): pulseeffects-WARNING **: 08:27:42.817: pitch plugin was not found! (pulseeffects:25896): pulseeffects-WARNING **: 08:27:42.817: reverb plugin was not found! (pulseeffects:25896): pulseeffects-WARNING **: 08:27:42.820: multiband_compressor plugin was not found! (pulseeffects:25896): pulseeffects-WARNING **: 08:27:42.820: multiband_gate plugin was not found!