Probably already screw up, as both the TRS app and website don't accept ARN.
But just want to make sure: invoice shows GST in AUD, but the company (overseas) doesn't have an ABN, only an ARN.
In such case the purchase is not eligible for TRS?
(Guess not if can't even get it into the app, but maybe there's way around it, who knows, no harm asking I guess).
You probably already know the answer.
Also I believe purchases from overseas are not eligible, even if they attracted GST.