They requested exemptions from the Australian government, but to no avail.
"I tried to follow my dreams, but Covid had other plans for me," Monnery tells the Herald on Sunday.
And it had been like a dream for the 24-year-old, born and raised in Wellington but living and working as a singer in Auckland, after she was scouted by the show in October to audition for a part.
She made it through auditions and started filming with the show in February, being selected to join the team of American singer songwriter Kelly Rowland, of Destiny's Child fame.
She made it through two rounds before the show stopped filming in March and she had to head home.
She found out her fate in May, but had to wait until her round had been screened on television this week before she could speak publicly about it.
"Covid has affected my Ella," Kelly Rowland said in the show. "She's in New Zealand and like me, she can't travel."
Monnery - who has been singing since she can remember - said she had a "little cry" when she found out she couldn't go back.
"I was so gutted. My whole year had been planned around that."
Initially she and Jago-Ward fought hard for exemptions from the Australian government, but these were ultimately turned down.
"They let the whole Warriors team go, but not one female singer," Monnery said.
But over the last two months, seeing the impacts of Covid-19 around the world, she had come to terms with the situation.
"Seeing what everyone is going through, we are all struggling, but I am alive and healthy, and I can still sing, do what I love."
To be selected personally by Rowland was "amazing".
"She is so gracious and down to earth. I am absolutely disappointed to not see her again and work with her. I've also made some pretty amazing friends, so it sucks knowing I'm not going back to be with everyone again."
Jago-Ward, who was part of Boy George's team, had been on the show five years before, and told the show while he was disappointed he was "more gutted" for Monnery.
"This was her first go around, and I hope she'll consider coming back for more."
Monnery told the Herald on Sunday the show had indicated all things going well she could potentially return next year.
"I have unfinished business."
In the meantime, she said she had been enjoying the imposed downtime due to the lockdown, and has a few shows and recording sessions lined up.