second request for substitution?
 

Fed rules- R6 illegally attempts to substitute for R1. The substitution is authorized and before the beckon for serve, is recognized as being illegal. Team R is penalized with unnecessary delay and must use one of it's two time outs. R1 is put back into the lineup, can Team R make a legal substitution at this time ?

Yes, they can sub either during the TO or immediatedly after.

NFHS and USAV: no sub allowed. This is a second sub request without a rally (USAV requires a completed rally) being played. A timeout does not buy you a new request. NCAA can have a new request if there's a timeout, and the sub gets administered at the end of the timeout.