Cindy, I have installed OPC 2.4.0 on Zen Cart 1.5.7d

When I get to the Checkout page and enter all my details, then click 'Save Changes' nothing happens and everything remains greyed out. All the details are entered correctly as well.

There is a box on the right of the screen that says 'Bottom Instructions', but it has nothing in it.

I have attached an image.

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Also when I turn OPC off and use the default checkout, that works ok.I have a DEBUG file, but I would need to send it to you as it contains personal information. So can I'll send this by PM.