Repository › Forums › Support › WooCommerce Extended Coupon Features PRO › Undefined index: key in WJECF_WC.php line 88 › Reply To: Undefined index: key in WJECF_WC.php line 88
This notice can be ignored. I will fix the notice in the next version.
What do you mean by ‘and so cannot add to basket’? If you disable WP_DEBUG_DISPLAY all should work fine.