Own and other's skins are all default(alex and steve)

My own and other's skins look like the default, and I am unable to figure out how to fix it. Some times it works for one to two people skins, but mostly doesn't work, which is very annoying at times. I have gone as far as to delete minecraft to see if that would help, yet nothing works. Is it possible there might be malware affecting it? I have had this issue for years. Thanks for all your help.