Is This A Bug in MCPE Marketplace?

Hi there.
Recently, I wanted to download an Original Music Pack to be added in my game.
Right after I clicked on the pack, it showed a pop-up called 'xbox.signinFirst' and the messages.

I'm just wondering, is this a bug or not? Or do I need to be sign in with my Xbox account? ( In the screenshot )
Thank you for taking your time viewing this report.

Edit : I tried to sign in a lot of times to get this pack, but I still failed to be able to sign in or get the pack for free..

Phone Used - Sony Xperia XA Dual