I lost access to all my iTunes purchases

I had an iPhone 8. I have purchased hundreds of songs. I bought an I phone 12. Everything transferred for a couple days. Today I lost access to 50% of my songs. I could still see on iTunes, where I purchased them but I couldn’t download. I read to log out and back in. I did that and now I lost 95% of my music and I can’t see any that I purchased.