Add the following to your proguard-rules.pro:
proguard-rules.pro
# ChatSDK-keep public class sdk.chat.**, sdk.guru.**, firestream.chat.**, app.xmpp.**, co.chatsdk.** { public protected *;}-keep class org.ocpsoft.prettytime.i18n.**-keep class .R-keep class **.R$* { <fields>;}# End