If you use the Edit Individual Documents facility from the Finish & Merge drop down in the Finish section of the ribbon, does the document that is created contain "images" of your envelopes with the addresses in the expected position?
What happens if you print that document? To plain paper?
Possibly on the Print Options tab of Envelope Options dialog, you will need to change the Feed method, orientation setting so that it matches where your printer wants you to feed the envelopes to it.