I'm pretty much in the same boat.I've already had to re-create all transactions since last September (beginning of the FY) with foreign suppliers - not too many...
Support were very helpful - I had to use the Sample File as a starting point as for some reason QBO would not accept the word "Stock" from my file but did accep...
I'm having the exact same issue when trying to Import Items with QuickBooks Online Plus, and I do have Track Stock on hand enabled. What else could I be missing...