I am trying to access my cross-progression on PC

ZinixKp​ Your Apex progress is tied to the EA Account it was earned/progressed on, (which in your case would be your old EA Account), so if you were to change which EA Account your Xbox Account is linked to, you will lose access to your Apex progress as that cannot be transferred, (or merged), to the newer EA Account.

• Where is my Progress? - An Apex Account Overview | EA Forums