Invoice approvals are not routing to next participant

Example, when an invoice is created by A & B, the approval should route to person C

then in next participant, there are rules based on natural account used in the invoice. This is triggering correctly.

In the first participant itself, we have written another rule like, if invoice is not created by A & B, the approval should route to person D.

Then again it should route to approval based on natural account through next participant - But in this case, it is just stopping with person D. It is not routing to further approval based on next participant.

What could be the reason