If you are seeing a "version mismatch" notification, that means that RiftCat application is installed in different version than VRidge mobile application.
This usually happens when one of the apps is updated while other is not or when one of the apps is updated to Beta channel while other isn't.
There is a chance that the apps will connect and work that way but most likely they won't.
To fix this issue - you have to update both applications to the same version. Make sure that your mobile VRidge application is updated. RiftCat desktop application should update on startup to the latest version on the selected channel.
There is a possibility that you have selected Beta channel for VRidge app or RiftCat desktop client. In that case, make sure that both apps are installed on the same update channel.
RiftCat desktop app update channel is selected within Configuration -> VRidge Settings -> Updates (tab) -> Update channel
Select the appropriate update channel for the version that you would like to use. Remember that while Beta channel might have the latest features, it might have bugs, errors or it might be generally unstable.