Hi! That’s probably because you forgot to add proper annotation processor dependency to your build.gradle file. Try adding this:

implementation "android.arch.persistence.room:runtime:1.0.0"
annotationProcessor "android.arch.persistence.room:compiler:1.0.0"

Or if you’re usign Kotlin, then use kapt:

implementation "android.arch.persistence.room:runtime:1.0.0"
kapt "android.arch.persistence.room:compiler:1.0.0"