The notch filter settings ask for more filters than the board allows

What ArduPilot says:

• Config Error: Too many notches: N > N

A harmonic notch is really many small filters: the harmonics chosen, times the notches per harmonic (one per motor with the per-motor option, and two or three times as many with the double or triple option), times the IMUs it runs on. The first number is what your settings add up to, the second is the limit built into this board's firmware. The board stops at start-up with a configuration error until the count is reduced.

What to do, most likely first

1. Too many harmonics are selected together with per-motor or multi-notch options.

   CheckCount the bits set in INS_HNTCH_HMNCS and read INS_HNTCH_OPTS (double notch, triple notch, multi-source, all IMUs).

   FixKeep only the harmonics your log shows, and clear the double, triple and all-IMUs options one at a time until the first number is no larger than the second. The parameters can be changed while the error shows; reboot after each change.

2. A second harmonic notch was switched on with the same generous settings.

   CheckINS_HNTC2_ENABLE is 1.

   FixGive the second notch one harmonic only, or set INS_HNTC2_ENABLE to 0 if you do not need it.

Parameters to look at

Where to do it:Setup & Tuning Guide