I'm getting this error on 2031. Manual method installed and .ocmod installed correctly

Notice: Undefined index: pre_order in /xxxx/xxxx/xxxx/xxxx/system/modification/system/library/cart.php on line 26

Hello Steve2,

Can you please make sure that you don't have any errors in your ocmod log and that the module's xml file has hooked correctly to all of the files? Also, you'll need to add the module to the desired pages from Desing >> Layouts.

I hope this helps!