BARCELONA, Spain — The Trump administration sent a delegation to Spain this week to make its case against the Chinese technology company Huawei at one of the world’s biggest tech trade shows.

But the event, called MWC Barcelona, ended up being favorable ground for the Chinese maker of telecom equipment.

Of the more than 100,000 attendees and 2,400 companies at the event, most ignored the efforts by the United States to impose a ban against Huawei for security and surveillance risks.