The contest between Hughie Fury and Michael Hunter is once again called off.
The fight was scheduled to take place on October 29 in Birmingham.
Fury is dealing with issues related to lingering complications connected to COVID-19 and was advised by his doctors to withdraw.
Their fight was initially scheduled to take place in July, but Fury withdrew from the fight with illness.
Fury has been out of the ring since last October, when he stopped Christian Hammer.
"I feel weak with no strength," Fury said in a statement
"I am a professional boxer who needs to fight in order to pay my bills and to live. But I have been out for over a year now and, to my frustration, I have been advised by doctors to take total rest at the moment because I'm suffering symptoms of long covid.
"I feel weak with no strength. I've had all sorts of checks and they've diagnosed me as having long covid symptoms. It is frustrating but there is nothing I can do if my body's not allowing me to train. I'm going to take time out for the rest of this year and pick up again next year when I've rested properly.
"I have had 29 bouts, I'm ready for big fights and my promoter has guaranteed me a big fight upon my return. If that's Michael Hunter next, that's fine. If it's someone else, that's fine as well. I think everyone knows I will fight anyone as I have done over the years."
His father and trainer, Peter, added that his son is "sapped of all strength."
"Life brings all sorts of obstacles and boxing is no different. Hughie is feeling sapped of all strength and the long covid diagnosis means he's taking complete rest away from boxing for the rest of this year. Health is more important than money or trying to keep everyone happy," Peter Fury said.