Documenting the answer for posterity. The crash was reported as:
Caused by: java.lang.NoClassDefFoundError: com.nextpeer.android.R$style
This happened because the package name in Nextpeer's AndroidManifest.xml (Assets/Plugins/Android/Nextpeer/AndroidManifest.xml) was changed (to the game's package name, in this case). Reverting the package name back to com.nextpeer.android
solved the issue.