Order Confirm not working

Hi, I am new here and set up my store on opencart.

I have installed the payment module as cash on delivery, and shipping as Pick up in store or free shipping.

But after filling all the details on checkout... while clicking on order confirm.. it is not going through.

I tried with standard paypal too, it takes me to paypal page, but order is failed and didnot go through.

Please help

Thanks,