You’re missing the networks section in your audiobookshelf service definition - add networks: [nginx] to your audiobookshelf service to actually connect it to the network (just defining the network at the bottom doesn’t automatically attach your service to it, which is why npm can’t reach it and gives you that 502 error), and if you’re an audiobook fan you might wanna check out the soundleaf app for ios which works great with audiobookshelf.