Hi,
Can you please re-download HikaShop 2.3.4 ?
It should fix the paypal problem.
About the warning, you can edit the plugin "plugins/hikashop/group/group.php" (after the update) and replace the line
if($product->product_group_after_purchase != 'all' && $product->product_group_after_purchase != '') {
By
if(!empty($product->product_group_after_purchase) && $product->product_group_after_purchase != 'all' && $product->product_group_after_purchase != '') {
I'll remove the warning.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.