The 22-year-old Burundi international, who extended his contract with Cosmos in June, spent a part of pre-season training with the Urban Warriors and even featured in some of the PSL club's friendly matches, but had to return to Cosmos when the two clubs failed to come to a financial agreement.
"That deal failed." Sono tells Kickoff.com.
"Ajax didn't agree with the price so he had to come back to Cosmos. That's not the problem to us because we have a three year contract with the player, so no problem. He is here playing for us."
With Rivaldo Coetzee having being sold to Glasgow Celtic it remains to be seen if Ajax will try to come back with another offer.
Ezenkosi started their National First Division season with a 1-0 loss to Highlands Park last weekend and will be looking to redeem themselves in their next game against AmaTuks at Olen Park on Sunday.