Interactions performed on tablets use the interaction class PegaCA-Work-Interaction-Mobile. Various rules related to interaction managment have been specialized in this class. You should ensure that your tablet interaction class inherits from PegaCA-Work-Interaction-Mobile.
Pega Customer Service uses the circumstance template CPMPortalType to determin when the Pega Customer Service Interaction portal is being accessed from a tablet. Various UI rules (in class CPM-Portal) are circumstanced to specialize them for tablets, that is when CPMPortalType = CPMInteractionMobilePortal.
Please check below CS 7.22 implementation guide for the details: