Sorry for delay in replying. I will need to review your installation. I am currently a bottleneck here, and it's my fault for the delays. Sorry.
Please Private Message (PM) me access to the site and Ogone so that I can review the settings and issue. Link to PM me is in my signature below. Also PM me instructions with links to test the failure. The only thing I can tell is that we use Ogone with settings like in our manual and it works well here and on our test-site. So there must be a difference somewhere, to find.