Since you are creating an RFX from sourcing cockpit. this issue is related to the hierarchy templates assignment.
Go to SPRO -> SRM Server -> Cross-Application Basic Settings -> Service Procurement -> Activate Service Procurement.
Here you assign hierarchy templates HIER_SE or HIER_SRM to RFX transaction types, depending on the scenario that you are working.
Hierarchy template to be used when the RFx is created based on backend purchase requisitions.
Hierarchy template to be used when the RFx is created from a local shopping cart in SAP SRM or when a local RFx is created.
So, when a backend PR is sent to sourcing cockpit, only those transaction types that have HIER_SE assigned will be listed.
When a local SC is in sourcing cockpit, only those transaction types that have the hierarchy template HIER_SRM will be listed.
I hope it clarifies.