Hey there! @glc650,
Thank you for reaching out for assistance with your Wemo Mini.
Can you please provide us with the model code of your device located on the back? You have already mentioned the device is setup running v4 in the Wemo Belkin Application.
When adding to Smart Things, Are you using the pathway (+) > Device > Belkin App> Supported Devices> Smart Outlet and following the on screen instructions automatic detection?
Additionally, you can find more discussion on adding the Wemo Mini to Smartthings here in this thread: WEMO Mini does it work with ST?
I hope this message finds you well!
^SamsungZell