The Principle of Contingent Causation: The Impossibility of Infinite Regress.

[Angrboda]

Look, its fairly straightforward:

1. A series formed by successive addition can never be an Actual Infinite.
2. The temporal series of past moments is a series formed by successive addition.
3. Therefore, the temporal series of past moments can never be an Actual Infinite.

If you want to challenge this argument, you need to show one premise is false. Which is it?

And two, as pointed out has an ambiguity of terms, which as I pointed out earlier, either leads to a different conclusion, or makes the conclusion a non sequitur. Since that exhausts all the possibilities, the conclusion is not true.

If you need something more precise, two is false as an infinite past isn't formed by successive addition; it simply is infinite.