Since you made a copy of your sample, it will automatically be assigned to new waveform, but that waveform is not yet assigned to a voice. You need to create a regular User Voice that uses your new waveform. Here is how.

Sample Voices are available only in the song or pattern where they were created. One of the advantages is that you have up to 16 Sample Voices per song that can be .

If you go to Sampling Mode, and press edit you should be able to select the keybank and waveform that contains the loop you copied. Remember that the loop only plays back on one note so check C3 or the note you selected as the original keybank.

You could then slice the loop and then you would be able to change the tempo.

You can go to Voice mode, select a user voice you can do without, initialize that voice using the job mode and then go to Element Edit, F1 -SF1 - Wave . Select User as the waveform Bank and call up the different waveforms until you hear the one you want to use. Pres store to store your voice and the call that voice up in your Mix (or from Voice in Rec Setup)