What are the rules on revokes in bridge game
In duplicate bridge under ACBL rules, revokes that are established are not corrected until the end of play. As such, an accusation of a revoke that was in error would not lead to any benefit for the accusing side, and so no penalty would be assessed them unless they were acting in an unsportsmanlike manner in the eyes of the director (either the manner in which they made the accusation, or in excessively making baseless accusations, though the latter I've never seen be an issue).  

Revokes that are not established are typically resolved simply by asking the player if they have another card of the suit they showed out of; if they assert they do not, then play would continue, and as before the revoke could be ascertained at the end of the match (in which case it is treated as an established revoke).

See ACBL law 61B:


  B. Right to Inquire about a Possible Revoke
  
  
    
    Declarer may ask a defender who has failed to follow suit whether he has a card of the suit led.
    (a) Dummy may ask declarer (but see Law 43B2(b)).  
    
    (b) Dummy may not ask a defender and Law 16B may apply.
    Defenders may ask declarer and, unless prohibited by the Regulating Authority, may ask one another (at the risk of creating unauthorized
    information).
    
  


Note 3:; defenders may inquire to declarer or each other whether they are out of a suit (and I commonly do this;  "No spades, partner").  However, unless you are extremely consistent in how and when you do this (meaning, unless you do this every time your partner first shows out of a suit, and do so in the same tone every time), you may be creating unauthorized information.

In that case, a penalty may be assessed by the director if it is determined that UI existed and may have been acted upon.  This will depend on the situation, though, there is no explicitly prescribed penalty for UI other than attempting to rectify the situation.

Thus, if a defender believes a revoke has occurred and calls the attention of the table to it, and is incorrect, that UI may exist; that is where a penalty could come.  Declarer would not be penalized (unless he/she acted in an unsportsmanlike manner) as declarer can never benefit from UI.