Apple Music Sign-in | Windows 10 Laptop

Try clearing your cached data and cookies. I had a similar issue in Chrome recently across multiple browsers and initially assumed it was going to be a server side issue rather than the same caching issue across a number of computers and platforms.

tt2

Here is a similar thread suggesting the same solution, where it works for at least some of the people posting there:

Apple music login box on browser disappea… - Apple Community.

Is this https://music.apple.com or the Apple Music app? If it is the app can you at least sign into the website as a short term workaround? Have you tried reinstalling the app?

tt2

You keep giving the same reply to everyone with the same problem, it doesn't work, and this is not a solution.

It's not the same solution as clearing cookies, it actually worked, so thank you for the extra effort and for pointing out that thread.