When I play De-Synchro to make combo plays with Infernities my monsters don't get special summoned.

well you didnt specify what happend with the monster after used by Synchro summon

maybe
the Synchro Material Monster(s) is removed from the Graveyard and then sent to the Graveyard again,
then it is no longer considered a Synchro Material Monster(s) and you cannot Special Summon any monsters with "De-Synchro".

lot of things can happen causing the monster not coming back to field

you should specify it

If you can attach a replay , it will make things clearer.