WASHINGTON — A Florida fund-raiser planned for April that was to feature Melania Trump has been called off after state regulators there concluded that the company working with the former first lady to organize the charitable event had not properly registered to solicit contributions.

Mrs. Trump had announced in late January plans for what she called “Tulips & Topiaries,” a gathering at an undisclosed location in Naples, Fla., that would feature an “elaborate flower garden with tulips” and “delicious hors d’oeuvres alongside tea and bubbles.” Tickets were put on sale for as much as $50,000 for a VIP table, with the money, she said, slated to provide scholarships to children emerging from foster care.

But Whip Fundraising, a consulting firm that helped organize the event, only registered as required by the state in recent days, after Florida officials began investigating the matter. Florida requires certain organizations that ask for charitable donations among Florida residents to first file with the state and then report how the money will be spent.

“They were not registered as a professional solicitor or a fund-raising consultant, and they are working to rectify that,” said Erin Moffet, a spokeswoman for the Florida Department of Agriculture and Consumer Services, which oversees charitable organizations in the state.