Cannot activate on multisite client domain

I’d verify first that you’ve got a good install of Pods. Clear out your install directory of Pods and re-install again and then see if you have the same issue.

This also might be related to Network Admin rights vs. regular client domain Admin rights. By default only super-admins will have access to Pods Admin on Network Activated Multisite install. You can enable admins or other roles to access it with Roles and Capabilities component (Pods Admin, Components, Roles & Capabilites) or with the Members plugin.