HTTP ERROR 400 when Exporting data

I’ve used Smart Forms for a long time and have bought the pro version. On other hosting sites I have no problems, but I just set up Smart Forms on a site with Ipower.com, and everything works (emails, collection, view data), but I can’t export. When I select the items and click “Export,” I get this error:

This page isn’t working
If the problem continues, contact the site owner.
HTTP ERROR 400

I contacted ipower support and they went through a bunch of stuff and finally thought they solved it by having me click “export” when looking at the form (where you can also edit the form). I thought it was the solution, so quit chatting, but it was NOT the solution.

Any ideas?