engineer requiring that we go through architect

We paid our architect the agreed-upon sum for schematic design and getting permits approved by the DOB and now he says he doesn’t want to do anything further. The engineers with whom we signed a contract (but who at the time did not request a deposit) says that “the flow of information from GC/client to the design team must go through the architect.” Do all engineers require this? Some of the work for which we require an engineer is part of the current application approved by the DOB (mainly, rebuilding the stairs to meet code). Some of it has not been applied for yet (on the advice of the former architect and our expeditor), mainly, deck and opening the back first floor wall. Any advice as to how to proceed? For the interior stairs, since the original architect’s name is on the project, can we even get a new architect?