"Where are the tickets?"

Translation: Ble mae'r tocynnau?

[aussienerd]

Why is it not ydy here?

[ibisc]

The question words ble/lle?, pam?, pryd? and sut? when it means 'how?' are followed by mae, bydd, roedd, etc rather than by ydy/yw/sy, fydd, oedd, etc.

It is to do with them being of an adverbial nature.