I have added the code but still not working. So am I the only WPLMS customer who is experiencing this problem? Is there no other way around this?
I would recommend to add a link in menu for cart page,
When someone book a slot, he can click on cart page link and from there checkout page
The other alternative is to skip cart page and directly redirect on checkout page
There is a setting for that in wp-admin > WPLMS > Miscellaneous > Direct Checkout