You need to get the error code read, so you know what is causing the problem instead of randomly throwing parts at it. The ECU is very rarely the cause. In this case it sounds like lack of pressure. As the accumulator is new, it should be good. Did you do a full bleed as per RAVE? Normally that's not necessary, but because your original symptoms were a spongy pedal, there may very well be air (or nitrogen) in the system.