Cannot download music previously uploaded to iTunes Match

A number of years ago I signed up for I-tunes Match. I then uploaded all of our previously owned music (CD's, etc.) into I-tunes Match. Since then, any new music we've purchased has been through the I-tunes store. For years it's worked seamlessly as we could play all of our music through our homes entertainment system. Like most people, we've upgraded/changed our Apple devices as new products emerge. However, we now cannot download some of the music we had previously uploaded to I-tunes Match. There doesn't seem to be any rhyme or reason as to which ones will download and which will not, except that it is exclusively the music we uploaded that we previously owned (our old CD's, etc.). Any music purchased through the I-tunes store has no problem downloading. Any thoughts?