make sure the parameter in question is the one selected for automation and its "Record" LED is lit to red; if the automation curve doesn't change, or no new nodes appear on the curve while you're turning the MIDI controller knob, then it probably isn't the one you've selected as current or the MIDI controller there assigned is not the same you've currently selected on that track and plugin. please double-check.
oh. and which option are you on? a. or b.? take note that option a. is the recommended way for capturing automation; on plugins option b. is not quite the same, besides being global configuration, it reads from the performance "cooked" MIDI stream instead of the more general control one. whatever. for automating plugins use option a. always.
recording automation occurs in real-time, while playback is rolling; no need to arm the track for [R]ecording whatsoever.
make sure the parameter in question is the one selected for automation and its "Record" LED is lit to red; if the automation curve doesn't change, or no new nodes appear on the curve while you're turning the MIDI controller knob, then it probably isn't the one you've selected as current or the MIDI controller there assigned is not the same you've currently selected on that track and plugin. please double-check.
oh. and which option are you on? a. or b.? take note that option a. is the recommended way for capturing automation; on plugins option b. is not quite the same, besides being global configuration, it reads from the performance "cooked" MIDI stream instead of the more general control one. whatever. for automating plugins use option a. always.
recording automation occurs in real-time, while playback is rolling; no need to arm the track for [R]ecording whatsoever.
hth.
cheers