The driver for the 6251 is DAQmx and Elvis uses the Elvismx driver. If you follow this KB you will find each driver and more documentation about the error you are seeing. Let us know how this goes.
Is that for the NI Elvis II? I have the older Elvis board
I installed the lastest ElvisMX 16 and MyDAQ 16 and the instrument launcher still says no supported devices
Did you check the Device's name in MAX? both names should be the same, in MAX and Elvis
Does the error appear when you click on "check"?
Did you run the DAQ Diagnostic Utility? What was the result?
If you're working with a traditional ELVIS device, rather than the ELVIS II, ELVISmx is not going to be compatible, per this compatibility chart.
This link will take you to the list of downloads pages for tradition ELVIS drivers. Generally we recommend downloading the latest drivers for your device, but make sure you double-check the readme before installing, to make sure that the version you're getting is compatible with the rest of your NI software.