Just as Donald Trump's inauguration concluded, Honduran asylum seeker Denia Mendez's phone buzzed with alarming news: the CBP One app, her lifeline to a new life in the US, was down.

Victoria Meijia Garcia, 31, opened the CBP One app at 10 a.m. Monday as she did every day for the past several months, seeking an available appointment with an asylum official. But today, the top of the familiar homepage blared a message that filled her with dismay.

President Trump has vowed to clamp down on immigration and undo Biden-era policies that he said were too permissive and blamed for allowing a large influx of undocumented immigrants. Here’s what we know about his policy changes.

The CBP One app has been highly popular, functioning as an online lottery system that grants appointments to 1,450 people daily at eight border crossings. These individuals enter the U.S. under immigration "parole," a presidential authority that Joe Biden has exercised more frequently than any other president since its creation in 1952.

Hours after Trump’s inauguration, his administration canceled appointments allowing migrants to enter the U.S. to request asylum, leaving many of them stranded on the U.S.-Mexico border.

Migrants who waited months to cross the U.S. border with Mexico learned their CBP One appointments had been canceled moments after Donald Trump was sworn in as president.

"The first 100 days are going to be the most aggressive, change oriented policy proposals and procedures that we've ever seen," KOAT political expert Brian Sanderoff said.

The CBP One app has been wildly popular. It is an online lottery system to give appointments to 1,450 people a day at eight border crossings.

The Homeland Security Department has scrapped a Biden policy that kept immigration authorities away from sensitive community places.

A host of local and national organizations preparing to counter executive orders signed this week by President Donald Trump say immigrants are vital to the social and economic fabric of communities.

Declaring illegal immigration a national emergency, Trump ordered the Pentagon to provide support for border wall construction