Unable to view rt struct even after installing slicerRT extension

I was trying to install slicerRT extension using extension manager. But it was giving this error.

Then I installed the extension manually from a file https://slicer-packages.kitware.com/api/v1/item/62c80d5caa08d161a319bcd6/download

But I’m still getting this while viewing my RT- Struct in slicer.

You have downloaded an extension for Slicer revision 30893 (Slicer 5.0.3). Please use the latest Slicer Stable Release (or the latest Slicer Preview Release if there is a specific fix or new feature you need) and let us know if you encounter any problems.