Dubois had scored a big knockout win over Anthony Joshua last September. His withdrawal led to Parker facing and stopping Martin Bakole inside two rounds instead.
In an interview with Podlounge UK, Dubois explained how it all unfolded:
"On the Thursday and Friday I started getting ill. My glands swelled up and my throat went. I started getting fevers and I was drained and tired. I can't put it into words."
The boxer called in a doctor from the British Boxing Board of Control to examine him. Despite Dubois wanting to go ahead with the fight, the medical professional advised against it.
"The doctor came to look at us, we called the British Boxing Board of Control doctor. I wanted to fight, I still wanted to carry on and fight but the doctor came and looked at me and spoke to Frank. He checked me out and examined me and said he wouldn't advise me to fight."
The doctor predicted Dubois' condition would worsen in two days. Ultimately, Dubois followed the advice of the doctor, his father, and his team to withdraw from the fight.
"He said in two days you'll be a lot worse. He said he wouldn't advise me to fight. I listened to the advice of the doctor, my dad and my team. They advised me not to go. I wanted to fight, I really wanted to go out there and put him to sleep, but sh*t happens."
Dubois stressed that he was fully committed to the fight and wasn't making excuses:
"I was 100% focused on that fight. I wanted to go out there and put him to sleep. We had the British Board of Control. You can ask them and their doctor and get the proof from them. That's what happened. I'm not making any of this up."
As for what's next, Dubois' future plans remain unknown. However, the IBF has announced that they'll order a mandatory defense against Derek Chisora. That fight could be Dubois' next move in the heavyweight division.