The African Global Economic and Development Summit took place at the University of Southern California from March 16th to 18th.
None of the approximately 60 invited guests from Africa were able to attend.
The problem was that none of the African delegates were able to get U.S. visas.
Humphrey Mutaasa from the mayor's office in Kampala, Uganda, had organized a delegation of 11 business leaders from Uganda to attend the African Global Economic and Development Summit at the University of Southern California.
He says it was a very high level group of leaders from private businesses, the Ugandan ministry of trade, chambers of commerce and the Kampala mayor's office.
"The delegation that was coming from Uganda to that summit was very, very disappointed," he says.
The conference was first held in 2013 and seeks to strengthen business ties between U.S. investors and African companies, says summit chairwoman Mary Flowers.
Visa problems have been an issue before, she says. In the past, she says roughly 40 percent of African invitees are unable to get the papers they need to attend, mainly due to a combination of red tape and bureaucracy.
"This year we were thinking there are going to be some rejections but some will still come," she says. "But it was 100 percent blocked across the board."
It's hard to find out exactly why.
Delegations were invited from 12 countries across the continent. None of them were from the three African nations (Libya, Somalia and Sudan) covered by President Trump's executive order temporarily banning travel from 6 majority Muslim countries.
Flowers speculates new vetting procedures put in place by the Trump administration are discriminating against travelers from Africa.
"Obviously because this has never happened before," she says of the inability of anyone to come.
The White House has called for "enhanced screening and vetting of applications for visas" worldwide as part of stepped up efforts to keep out terrorists.
A State Department official on background tells NPR that they can't comment on any individual visa applications but says all applications are screened on a case-by-case basis. And the eligibility requirements for getting a visa haven't changed.
Some of the African delegates to the summit say their visa applications were denied because they didn't show a compelling reason why they would return home after the event. Others say bureaucratic hurdles were so big that they were not able to submit a visa application in the first place.
Humphrey Mutaasa in Kampala says the online application is complicated. You can't even see how long the process will take until after you've paid a $160 application fee at a local bank. Then you have to wait a day to get a confirmation code to book an interview at the U.S. embassy.
"Then when you've finished that and you have the codes from the bank ... there are the challenges of internet connectivity," he says. "When you get online then the calendar [from the Embassy] will tell you the whole of February, there are no appointments, You can only secure an appointment after the 15th of March."
Which meant he wouldn't have a ruling on his visa until after the three day conference had concluded.
The end result of this year's visa outcome, says Flowers, is going to be fewer connections between American business and the continent.
"I don't know whether there's some secret message going to the U.S. embassies in these African countries but it's ridiculous," she says. "The [visa] process was already somewhat discriminatory against the African nations in the past. We don't know what the story is now but I do hope that America remains open to the world."