I am having the exact same issue in all my games using 15.1.1 and script 11.1.0. Games that monster and spell import worked fine in yesterday stopped working today. I was thinking maybe it was my account as I also lost all music sound in the client. Most likely an unrelated issue. I am wondering if maybe roll20 made a change to the api? I am able to import monsters via statblock just fine. I have not changed anything since they last worked with these versions.