Offer Compatibility Checker can be enabled for
Buy More Services wizard and
Upgrade screen of Customer CP as per Configuring Offer Compatibility Checker deployment guide article.
Can it be enabled for Online Store ?
It is not supported currently.
Feature Request #PFR-1256: "Office 365: Offer Compatibility checker in Online Store" has been addressed to Odin Development team in order to implement this functionality.
Please contact email@example.com or TAM to trace the status of the Feature Request.