This is a current limitation of SOLIDWORKS Simulation. Please see SOLIDWORKS Simulation Help topic "Connector - Spring".
The Enhancement Request to remove this limitation in future versions is documented in:
SPR 335159 - "Allow Spring Connectors between faces in SOLIDWORKS Simulation Nonlinear studies (currently only possible using vertices or points)"
To request this enhancement, please search for SPR 335159 in the SOLIDWORKS Knowledge Base (KB) and select 'notify me'.
In the meantime, you can create split lines on the faces and use the vertices at the split line intersections to define 'Two locations' Spring Connectors. Please feel free to contact your SOLIDWORKS Value Added Reseller (VAR) for additional guidance.