Install redirect after iThemes Security problem

I’ve had problems with redirect loops after changing something in iThemes Security (I think it was the table prefix).

My site was new, so I just figured I’d start afresh – I deleted everything, created a new database/user and reinstalled WP. I then updated the config file as per usual.

However the redirect continues and I can’t figure out why, given I deleted all the old files and database!

Any ideas?

Thanks