Box 16 in T4 empty

[Citizen001]

Ufile cannot calculate my tax return due to this error;
“You have employment income and are not exempt from paying CPP/QPP contributions. You should normally enter your CPP contributions (Box 16) or QPP contributions (box 17)in your T4 slip.”

even if i put exemption(rare!) in box 28. I keep getting the error. My employer says box 16 is really empty because my earning is $375 for couple of days work. 
Until bow I can’t file my tax

[Geo123]

HelloCitizen001, 

T4 slip - Box 28 - Exempt (CPP/QPP, EI, PPIP)
If the mention "Exempt CPP/QPP", "Exempt EI", or "Exempt PPIP" is displayed in box 28 of your T4 slip, simply select the item "T4 and employment income" from the "Left side menu on the Interview tab", and in the page "T4 slip income", for "Box 28 - exempt (CPP/QPP, EI, PPIP)", choose the appropriate exemption in the drop-down menu located to your right.  

If you need to enter another exemption, click on the "+" sign located on the far right of the screen to add another box 28.

[Papet]

Good day Citizen,

The diagnostic you are mentionning appears in the Warnings section.

Your return has been calculated.
Look in the MaxBack notes and analysis section.
You will see whether you are able to file your return.

You are unable to file your return elctronically only when a diagnostic is present in the Electronic Filing Errors section.