I’m not completely familiar with the TAI certification problem. What is the problem?

Is the Max 7 TAI identical to the 8 and 9 and just can’t get certified “as is” because more of the current problem is known, or is it a completely different system than the 8/9 and has its own new problems?

I thought lack of EICAS was the big certification holdup; is that fixed or waived, or grandfathered in ok?

I guess I’m asking is this a 7 problem, or a problem with the Max fleet as a whole?