I opened it cross the console to see the debug log. So it appear it have a permission failure with the new JRE include. In follow a copy of the revenant log.
Trying https://dl.pokemmo.eu
Got updater from https://dl.pokemmo.eu
Updater Verified OK!
//Applications/PokeMMO.app/Contents/Resources/pokemmo-launcher: line 201: //Applications/PokeMMO.app/Contents/Resources/../PokeMMO_Client/jre/bin/java: Permission denied
NOTICE: The installation was a success
xStartOnFirstThread set, revision 15773
//Applications/PokeMMO.app/Contents/Resources/pokemmo-launcher: line 30: //Applications/PokeMMO.app/Contents/Resources/../PokeMMO_Client/jre/bin/java: Permission denied
New java pid 3084