The kick is on C2 instead of C1.

This is due to a weird anomaly of Reaper. It displays all octaves one number too high in the MIDI editor and on the virtual keyboard. This is also true with all other virtual instruments used in Reaper. Nobody knows why the developers of Reaper decided to do it that way. In all other DAWs the notes match correctly.

However, there is an easy global fix for that, directly provided by Reaper. In Reaper go to

Options —> Preferences —> Media —> MIDI

and set MIDI octave name display offset to -1