New Zealand has granted US whistleblower Chelsea Manning permission to apply for a visa, while Australian authorities’ delay has already cost her the first in-person appearance on her speaking tour.

Manning’s tour has been thrown into doubt by the requirement of a special direction visa to visit New Zealand and the Australian government’s decision to issue tour organiser, Think Inc, a notice of intention to deny her a visa.

On Friday morning the Think Inc director, Suzi Jamil, told Guardian Australia the home affairs department had said “that the matter is their top priority and they are working on processing it”.

The Australian government has received numerous submissions arguing for it to overturn plans to bar her.

But on Friday afternoon organisers of the Sydney Opera House’s Antidote festival confirmed the home affairs department had given notice it will not make a decision in time for Manning to attend her first event on Sunday.

Manning will now be interviewed from Los Angeles live via satellite by journalist Peter Greste in a conversation discussing data privacy and surveillance, imprisonment, the suppression of information and ideas by power-structures, and transgender rights.

The Antidote festival director Edwina Throsby, said: “We are disappointed that Chelsea can no longer appear at Antidote in person, nevertheless we are pleased that Sydney audiences will still have the opportunity to hear her directly.

“As a high-profile public figure, her opinions, ideas and expertise on these matters is timely, and of genuine interest to our community.”

Manning is also due to appear in Melbourne on 7 September and Brisbane on 11 September.

In New Zealand, Manning is subject to “good character” provisions in section 15 of the Immigration Act 2009, as she was sentenced to a prison term of more than five years. In Australia, section 501 gives the immigration minister, David Coleman, the power to refuse a visa on “character” grounds.

Manning was released from prison in May 2017 after being sentenced in 2013 in violation of the US Espionage Act for disclosing classified government documents to WikiLeaks.

Her sentence was commuted by the then US president Barack Obama in early 2017, after she had served close to seven years in prison.

The Immigration New Zealand general manager, Steve Stuart, said in a written statement that while Manning was convicted of a serious offence and sentenced to 35 years’ imprisonment, “it was noted that her sentence was commuted by President Obama in January 2017”.

“The assessment noted that Ms Manning has not reoffended since her release from prison and the likelihood of her offending while in New Zealand is considered low. It was also noted that she has travelled to a number of countries to speak at similar events and appears to have complied with the terms and conditions of any visas issued.

“In reaching the decision the officer could see no reason to believe Ms Manning would not comply with the terms and conditions of any visa issued by INZ.”

However, an opposition MP, Judith Collins, said Manning had betrayed her country.

“Most likely, with the information that she gave, people lost their lives or were definitely put in danger. She is a traitor,” she told the AM Show.

The New Zealand prime minister, Jacinda Ardern, is said to have justified the decision to allow Manning in by noting that her views would be of interest and people should be allowed to hear her speak.

In Australia, the Greens leader, Richard Di Natale, Labor’s equality spokeswoman, Louise Pratt, and numerous human rights groups have lobbied the Morrison government to allow Manning in, arguing that free speech meant opponents of government policy should not be barred from entry.

The Australian home affairs department said it did not comment on individual cases.