Problem with iTunes not saving new content

I am using a MacBook Pro with MacOS High Sierra 10.13.6 and iTunes 12.8.2.3. I have been attempting to add new songs and other content to my iTunes library. I am able to add what I want and organize everything into folders and playlists. However, when I close iTunes and open it again all of the work organizing my content is gone and the Library has reverted to what it was before. I can't make any permanent changes. This happens for both users on my computer and also on my husband's computer (same OS and version of iTunes). My husband syncs his playlists to his iPhone 6 to use when he is away from his computer. He likes to update his iTunes Library on his Mac and then on his phone every month or so in order to listen to new content. This problem with new content not being saved is a relatively new one. It was working fine in January and early February. The last update to both computers was the Apple Security update in early February. I don't know if my husband has tried to update his iTunes since that update. But he is very frustrated that he can no longer update his iTunes library and then sync it to his phone.

Any help with this problem would be greatly appreciated.