To work out what is going on we'll need some more information. Can you describe where and how you are downloading files? (If many ways of downloading are broken, a single or perhaps 2 examples would be helpful.)

When you say "can't" - is there an error message that appears when you try, or is the option to download files simply not present? (A screenshot may help, but please make sure to redact any personal information as this forum is public.)