Impex not working for me... From VB 3.8.4 to VB 4.0.2
 

I am trying to run Impex... I put my customer number login in the import screen... it shows the following:

Successful
Redirecting

And then it sends me back to the customer number login screen... I can't get any further.

I have the following systems uploaded:

vb2
vb3
vb_36

is there a system for vb_38?

Also, what does the "define('dupe_checking', false);" function do?