ERG disabling on high power intervals

Hello. Over the last couple of days I’ve done three different workouts (low cadence intervals, The Wringer and Jon’s short mix). Each time, immediately I pass the gate from a low power interval (warm-up or recovery) to a higher power interval, ERG mode disables. It doesn’t seem to matter whether I pedal like the clappers or go hard and slow. (It kicks back in for the next interval, which is always a recovery one, but I get that that is normal.) I’ve done two of these these workouts before without problems. Any ideas as to what I’m doing wrong?