If you're unable to train mercenaries, check the following:
Is your Pub full? Logan's Pub has a limit of 20 mercs at a time.
Do you have enough products? Training mercs consumes products.
Are you tapping the right unit? Some mercs must be unlocked by reaching higher Mansion levels or completing missions.
Still not working? Restart the game and check for updates in the App Store or Playstore. If the problem persists, reach out to our support team.