Recently, I've written up a quick note explaining why an argument against platonism, based on the Church-Turing thesis and deployed by Olszewski (1999) doesn't work. It's here. Abstract below.
Olszewski  claims that the Church-Turing thesis can be used in an argument against platonism in philosophy of mathematics. I argue that the argument relies on the illegitimate conﬂation of eﬀective computability with computability by any means, and that even if it worked, it would not be an argument against platonism, but rather against any realism about truth-value of mathematical sentences.