When opening projects from older Music Maker 21-64 bit editions I got this "missing files"
For me the solution was to use the folder option. And do some searching until loop was found.
My Hardware is: Asus mother board ASUS P8 H61 R20 With Intel I5 and 16 Gb ram.w/ GT 710
Videocard and Maudio Delta 1010L with Windows 7 64 bit.. until recently I had mm2017, mmscore
and mm2019. I'm also using Acid music studio 9. Everything was running smooth until I
upgraded to music maker 2021. Hope this will help.