Vanina went to work in tears every morning last week. Monday was meant to resolve two-and-a-half years of anxiety, when she and the 3.5 million EU citizens in Britain could finally apply for the right to continue living in their own homes.

Yet the app that the Home Office is using to help decide whether people such as Vanina are entitled to “settled status” after Brexit simply added to her turmoil.

“I tried everything but I get to a certain point, and on the screen there is just a wheel going round and round. I can’t make my application,” Vanina, who did not want her surname published, told the Observer. The 46-year-old languages teacher, who was born in France but has lived in Yorkshire for 20 years, has called the helpline every day. “I have tried 12 different PCs, my phone, another friend’s. None of these work.”

However much friends and colleagues have tried to reassure Vanina, the fear that she might not be able to stay, that the computer might say no, has come to dominate her life.

Languages teacher Vanina, who has lived in Yorkshire for 20 years, is struggling with the Home Office app. Photograph: Paul Curzon

“It’s humiliating. To have to go through all this feels like a punch in the face,” she said. She has a son, a job, a mortgage. “If it doesn’t work and I overnight become illegal, what’s going to happen?

“This morning I just could not stop crying when I was at work. I can’t plan anything – my career, my home. It’s become unbearable. There isn’t a day I can push it away. You can’t stop thinking about it. That’s why I cry every morning on my way to work because I’m thinking, ‘What’s going to happen, what if this doesn’t work?’ This is my life.”

By the reckoning of Sajid Javid, the home secretary, the app has been a success. He told MPs this week that 90% of decisions had been made “as expected”. But the assertion has been met with scepticism by the3million, a group campaigning for EU citizens, which believes the only way the Home Office could arrive at this figure would be from the number of people challenging the app’s recommendation. And if 10% of decisions are challenged, that means more uncertainty for 350,000 people. A Home Office spokesman said a “tiny percentage” of people had been having problems and they were continuing to improve the system.

To apply for settled status, people need to use an Android app to confirm their identity using their passport, then go to the gov.uk website to provide evidence they have lived continuously in the UK for five years. Those who have an iPhone or other device, or aren’t online because they are elderly or disabled, can get help at one of 13 centres around the UK. The only one in Scotland is in Edinburgh, while anyone in Cornwall will need to make a trip to Bath. Even then, they will still need to go online to complete their application. [See footnote.]

In theory, all the 3.5 million should be granted settled status, except those with serious criminal records. Politicians have generally said they want EU citizens to stay, but EU citizens hear other things, too: Theresa May’s “citizens of nowhere” and “queue jumpers”. When Brexiter MP Mark Francois attacked Airbus boss Tom Enders last week, he invoked his father, a D-day veteran, saying he “never submitted to bullying by any German and neither will his son”. Words like that, they say, amplify their fears.

Journalist Philippe Auclair says the uncertainty has taken a physical toll. Photograph: Richard Gardner/REX/ Shutterstock

“We’ve been given verbal reassurances with nothing to back them up,” said Philippe Auclair, a musician and sports writer who has lived in London since 1987. He believes the process may lead to injustices similar to those experienced by some of the Windrush generation. “I’m not saying that we have suffered the same indignities and appalling behaviour by the Home Office that some people have gone through,” he said. “But let’s wait and see.”

The uncertainty has also taken a physical toll. “I’ve woken at 2am worrying and not been able to go back to sleep,” said Auclair. “I’m not exaggerating – that’s happened a dozen times. I know other people who have been far more affected than I have been. I can’t face it any more. We’re an invisible minority, the largest minority in the country, and yet nobody seems to think that we matter a jot.”

Dr Zain Sikafi, a GP who runs an online therapy platform called Mynurva.com, deals “day in, day out” with people affected by anxiety caused by their immigration status.

“The key one that everyone talks about is insomnia,” he said, with other symptoms being panic attacks, anxiety, eating problems, heart palpitations. “That leads to a deep sense of hopelessness, that there is no end in sight. That’s the worst place anyone could be in.”

The bland reassurances of politicians are matched by misunderstandings of friends and acquaintances. Cor Roest, who was born in Holland but went to an English boarding school and studied agriculture at the University of Reading, often hears friends say “but surely you’ll be all right”.

“All my mates are in England,” he said. “Most of them wouldn’t even know that I had a Dutch passport. My Dutch is pretty poor now – it’s not as good as my English. Okay, I couldn’t vote, but I like to think I know a lot more about British politics and history than most people. And suddenly there’s this feeling that you no longer belong.”

For Roest, it’s an urgent dilemma, as he now lives in Kenya, working for an agriculture development company set up by the Department for International Development. He has a British wife and two British teenage children, but at the age of 52 faces giving up his career to return to the UK before the deadline, although what date that is may depend on having a deal.

“I’ve got a statement from the DWP which lays out all my national insurance contributions. I’m hoping with clear evidence I’ve lived in the UK in the past for more than five years, someone at the Home Office will take a look and give me settled status.”

If he can’t get settled status, the only alternative would be to rely on his wife’s British passport. But she would need a job earning at least £18,600 a year and that threshold may rise. “The problem is, we just don’t know.”

• Note added 28 January 2019. According to the Home Office, feedback about the system and the app, to assist it in making any necessary changes before the scheme is fully opened by 30 March 2019, can be given on helplines 0300 123 7379 from inside the UK, and 0203 080 0010 from outside the UK. Support locations would increase from 13 to more than 50 across the UK when the scheme is fully rolled out, the Home Office said.