Hello Himay 88,
Thanks for using the Apple Support Communities!
I understand that you are not able to view an album that you added to My Music using the Apple Music service. The following article explains how to find and add music from Apple Music, but it sounds like you are already familiar with that process.
The part of the article I would draw your attention to, however, is how you are viewing your Music. It may be that you have the option enabled to only show music available for offline listening which could explain why you don’t see the album you added.
View just songs, albums, and playlists that you downloaded to your device
iPhone, iPad, and iPod touch: In the My Music tab, tap Library. Then tap any of the different views (Artists, Albums, etc.), and turn on Only Offline Music. A message that says "Showing only music on this [device]. Show All Music." appears at the top of the screen. Tap Show All Music to see all of your music.
Add music from the Apple Music catalog to your library on your iPhone, iPad, iPod touch, Mac, or PC - Apple Support
Cheers!