When manifesting Canada Post, you might come across the "Group XXXX shipment count X does not match count on Canada Post side X" error.
This problem happens when orders are not manifested in due time.
The manifest process has to be done at least once and when closing the day (even though you can do it as many times as necessary throughout the day).
Most of the carriers don't support manifesting orders from a day in the past.
You will not be able to solve this issue by yourself.
Please contact firstname.lastname@example.org and include this message in support request.