2001 Dodge Caravan Axle won't seat fully

I'm replacing the drive axles on a 2001 Grand Caravan Sport with the 3.3 Flex engine. The driver's side went off without a hitch, but the passenger side is giving me problems.

I'm unable to install the axle fully; when inserting it, it stops cold about an inch/inch and a half from fully engaged. I've pushed it, rotated it, tried installing it with the snap ring removed, tried tapping it in with a hammer and block of wood (gently), all to no avail.

I can't get a straight look into the differential because there's no clearance, but I've looked with an inspection mirror and don't see any obvious problems that would prevent the axle from being inserted.

It's a brand-new axle ordered online; I've taken it to my local parts store and compared it with both new and remanufactured parts to confirm I have the right fit.

I'm largely out of ideas; have any suggestions?
Thanks.