Bunq support responded to my request - I had a sub-account which had received interest for a couple of months, and I have screenshots of my configuration to receive interest. However I was told as the account was not a "Savings account" the interest payments stopped. I feel like this was something that went wrong with the December update as this was working OK for me.
Anyway, I had to create another new sub-account, mark it as a savings account, and should see interest next month