Box 16A (CPP2) is for non-Quebec residents, Box 17A (QPP2) is for Quebec residents.  I just tried completing my taxes again based on the comment in this thread that the issue seems to be fixed, however I am still getting the same error 90308.  I also read "make sure you update Turbo Tax", how is this done if I'm using Turbo Tax online?  I'm assuming this error is still not fixed.

Verify the T4 Slip Data:
Check if box 16A (Employer’s QPP Contributions) is mistakenly included for
Correct the entries: If the employer mistakenly included box 16A for a non-Quebec resident, remove it from the filing. Resave and resubmit the return.

We are aware of this issue, and our development team is working on a resolution. We appreciate your patience.

For anyone else still having this issue, the max amount box 16A can have in it is $188 or it messes up. Change box 16A to say $188 and add whatever was more than that in that box onto the total in box 16 and it will work. After making those changes it finally worked for me to file! Yay!

I was having the same issue. 
I am NOT a Quebec resident and removed the $188 from Box 16A. 
Now box 16 and 16A equaled lines 30800+22215+44800 and the Netfile went through.  
C’mon Ttax… you need to do better. 

Same Problem here but I don't have any number in Box 16A ! Just two T4s with amounts in Box 16 .

I still have the same Netfile error. I do not wish to proceed with simply "not entering" box 16A from my T4. These are CPP contributions I have made. (16A – Employee's second CPP contributions – Employee's second additional CPP contributions (CPP2).)

Is the over payment not calculating properly? my line 44800 remains zero. 

Something remains incorrect. When will this be resolved?

We are aware of this issue; we are working with the CRA for a resolution. We appreciate your patience.

Hey, I am having the exact same problem. Is that allowed if we just removed $188 from box 16 A just to make the lines all equal? Though it's not gonna reflect the actual T4

@triserenity 

The CRA has announced systems tax calculator errors that may affect your ability to file. These errors are affecting all CRA certified tax software across Canada.

TurboTax is in direct contact with senior Government of Canada officials at CRA, underscoring the urgent need for accountability and decisive action to resolve these issues for our customers and all Canadians. 

If you see one of these error codes, please visit What does my NETFILE error code mean and how do I fix it? 

Thank you for choosing TurboTax.

This is so frustrating.  I am not the only person who is experiencing this error.  It is like Turbo Tax has flipped the CPP and QPP.