The Public Transit tax credit is what is known as a non-refundable.
This means that if you are not taxable, that is you have no taxes owing, then this credit won't increase your refund.
Very similar to the way tuition works.
I'm not sure if this is the case with you, but it would explain what you are seeing.
I checked the calc for the Public Transit tax credit and it worked for me.
The Public Transit tax credit is what is known as a non-refundable.
This means that if you are not taxable, that is you have no taxes owing, then this credit won't increase your refund.
Very similar to the way tuition works.
I'm not sure if this is the case with you, but it would explain what you are seeing.
I checked the calc for the Public Transit tax credit and it worked for me.
I am taxable - I do not owe tax due to making a $16,000 contribution to my RRSP, but I have paid tax, so do have room to increase my refund. I saw this question 2 years ago, and it makes me wonder if your software does not work for/apply this credit. I am thinking of getting a T1 from the post office rather than paying for your service, since it doesn't seem to work properly.