Speaking to Sky Sports in the UK, Matchroom boss Hearn revealed that negotiations for a showdown between Joshua – the IBF, WBA, WBO and IBO champion – and Wilder, the WBC titleholder, for all the belts had broken down in recent weeks, with the American's team not responding to his messages.
Wilder is coming off a highly controversial draw with Fury in Los Angeles last December, which most observers felt he lost.
The result meant that Wilder retained his prestigious green belt and thus remains Joshua's preferred foe for the April 13 date at London's Wembley Stadium, according to Hearn.
Wilder and Fury were widely expected to meet again after the WBC voted to sanction a direct rematch, over-riding the mandatory challenge rights of Dominic Breazeale to Wilder's belt.
But Hearn believes there is still a chance that either fighter could be persuaded to face Joshua instead at the national stadium, with Fury firming as the more likely candidate.
"Well, to say Deontay Wilder's camp has gone quiet, that's saying it lightly," Hearn told Sky Sports. "Probably up to six unanswered emails now.
"It is frustrating because you walk out there on the street 'When's he [Joshua] going to fight Deontay Wilder?' It's like, whenever they want it, but sometimes the public want to believe a fighter on Instagram all day.
"If they wanted the fight, they would talk to me. They're not even talking to us. We've made offers, we've made percentage splits. Everything we can do, to try and make that fight," Hearn added.
"I think right now, there's more chance of fighting Tyson Fury. There's a man that knows he can have this fight, if he wants it. I've spoken to him. He knows if he wants to fight Joshua, it can happen April 13."
However, Fury's promoter Frank Warren dismissed Hearn's opening offer as "derisory" and insisted that he is still working on securing a rematch with Wilder.
"Any deal with Tyson Fury is gonna be a 50/50 deal, simple as that", he told UK radio station talkSPORT.
"When they did [Joseph] Parker, they settled on 67½/32½. You're telling me that Tyson Fury's worth [only] 7½% more than Parker? It's ridiculous," Warren added.
If a fight with Fury or Wilder cannot be made, top contenders Dillian Whyte and Jamell Miller, both promoted by Hearn, loom as likely options.
"There's Dillian Whyte, there's Jarrell Miller, but Joshua is back from holiday, he's started training now, he wants to know," said Hearn. "We've probably got 10 days to two weeks before we officially have to pull the trigger." Hearn told Sky Sports.
"All those guys that I've mentioned, particularly Wilder, Fury and Whyte – that fight is there for them.
"What I can tell you is, Dillian, I was with him this morning. He wants a great deal to fight Joshua. I don't blame him for that. He's been through a hard road to get where he is to No 1.
"He can wait and become mandatory at some point, but if Dillian Whyte wants to fight for the world heavyweight title on April 13, there is the opportunity for him to do so, right now."
Last week, Whyte said he received an "utterly ridiculous" offer to face Joshua and questioned whether his team was serious about making the fight.
But Hearn fired back, saying it was now "put up or shut up time" for Joshua's rivals and questioned whether any of them really wanted to face him.
"You want to win these four title belts, you believe you can beat Anthony Joshua, then let's go, but everyone wants to negotiate, and rightly so."