Canadian Permanent Resident who files taxes in the UK, wondering why I owe provincial tax the year I moved here?

I have been a resident of Canada since September 2019 and have permanent residency here as of December 2021, all of my work is carried out in the UK and I pay UK taxes.

I have filled my 2019 tax return in Canada but I was under the impression I would not owe anything due to the tax treaty in between UK & Canada, it seems I owe around $600 in provincial tax but not sure why this would be the case.

I have put all the figures together for my Canadian tax returns for  2021 & 2022 and it says I owe nothing for these. Why is it that I would owe for the 2019 year? I am freelance so the figures are different for each year 2019 was around $42k and then rising each year. 

Thanks in advance.