Go to your Payroll Withholdings report and select Accounts > Setup. Set the employee withholding accounts under the ledger indexed columns to Yes. They are currently blank. Once the ledger indexed is set to Yes then run T4 Summary again.
This problem was corrected in the latest service pack of 2.16 which is service pack three. I suggest that you download and install it on your system(s).
Regards to All.