The National Instruments myRIO requires to have the same Real-Time module installed on as the one that is installed with LabVIEW to be able to use, if an old version is installed on the myRIO then when you plug the myRIO in the “NI myRIO USB monitor” will disable LabVIEW from the menu (see fig 1), if you are using the latest version of LabVIEW then you will need to update the firmware* or use an older version of LabVIEW.
Instructions on how to update the BIOS and firmware on the myRIO: