How do I sync songs on my windows 8.1 pc to aiphone 11 ios 18.1.1 with apple music subscription?

When i go to play some songs on my iphone 11 using apple music i get a message sayin "this item is not synced across your devices" and the song title is greyed out. They played before, then all of a sudden they didnt. Itried syncing in itunes but nothing happens. My pc is windows 8.1 and I cant upgrade to 10 or 11, I dont have the $ for that. What can I do? If i cancel my apple music subscription ALL my songs on my iphone disappear. This is very frustrating!!