Multi-row variables are not cascaded through the order guide when ordering to Service Portal.
In the Service Portal deprecated widget is being implemented
In the service portal, you are using "SC Order Guide Deprecated" or customized from a Deprecated widget which is no longer the 100% supported version.
As the widget is deprecated the functionality of the widget has limitation one of them can be failing to load the values into the multi-row variable set.
Changing the widget in the "sc_cat_item_guide" page to the "SC Order Guide" is going to fix the issue.