Not The Welsh Labour Party? Has that a different title?
Why is it sometimes "Plaid Lafur" and sometimes "Y Blaid Lafur"? For example, when the sentence was "The Labor Party won a lot of seats," it marked "Enillodd y Blaid Lafur lawer o seddi" as wrong for using "y."
Like Dave Carver, I would like to know what "the Welsh Labour Party" would be as this is what I normally hear in English.
For 'The Welsh Labour Party' it would still be 'Y Blaid Lafur yng Nghymru'.
However, a phrase more often heard to refer to that party in the news and in the Assembly is 'Welsh Labour' - 'Llafur Cymru', or occasionally 'Plaid Lafur Cymru'
Why is it Nghymru and not Cymru?
Because "Yn" when it means "in" causes a nasal mutation, and "C" when it nasally mutates to "Ngh" and "yn" itself becomes "yng".
This is explained earlier in the course in the notes for the section on 'Countries'.