1) Unable to paste a voice that I copy or cut. 2) Unable to change voices of note.

Trying to separate these voices out onto separate staves so that I can clean up each part before rejoining them together into a single piano staff.

problem 1:
Steps:
1) Select any note.
2) Right click > Select > More...
3) Tick "Same voice" & change action to "Add to selection", Select "Okay".
4) Copy or cut the selected content.
5) Attempt to paste the copied content onto the empty piano 2 staff in the same clef and same measure.
6) Nothing happens.

Problem 2:
1) Select any note.
2) Right click > Select > More...
3) Tick "Same voice" & change action to "Add to selection", Select "Okay".
4) Ctrl+alt+1 to move content to voice 1.
5) Nothing happens.

I have attached the file I am working with. The content is from an XML file exported from a DAW that had the content split into two midi clips one for right hand and one for left hand. Ultimately the main problem is that when importing the XML file the notes have been split into many voices causing an abundance of rests. The notes need to be combined into a single voice which is proving harder than I was expecting and I seem to be experiencing bugs or limitations of musescore that I don't understand and would be delighted to learn about.

I'd be grateful if you could try it in this file, or point out the flaw in my steps. Thank you.