Hello @mdct,
have you checked this: https://blender.stackexchange.com/questions/16531/keying-set-failed-to-insert-any-keyframes
In this forum thread someone mentioned to enable the editability of a channel, maybe you have the same problem. If this is the case, this could help : https://docs.blender.org/manual/en/latest/editors/graph_editor/channels.html
Greetings,
tobles
