Ireland's Finn Lynch, Ewan McMahon and Liam Glynn all failed to book their tickets to the Tokyo Games after a highly competitive final at the Laser World Championship in Sakaiminato, Japan.
Australia's Tom Burton, who won gold in Rio, took the title ahead of his team-mate Mathew Wearn.
Carlow man Lynch was best placed of the Irish trio to achieve qualification heading into the final day - the top five unqualified countries were battling to go through this week - but he needed two single-digit results, which evaded him. Lynch ended the championship in 40th overall.
McMahon placed 50th on what was his his senior level debut at a world championship while Glynn - himself competing in just his second Worlds - finished inside the top 100.
There are now only two European places up for grabs for the Games, and they will be decided at the Sailing World Cup in Genoa next April.
"The result is disappointing, especially after such a strong season," said Irish Sailing's Performance Director James O'Callaghan afterwards.
"However, sport always has highs and lows. The key thing now is to bounce back and be ready for Genoa."
"When you see the strength of nations like Australia, New Zealand and Great Britain (who dominated the top 10 along with France and Germany) it gives you confidence that the 'one nation one team' approach is the way forward. We have a young team of three athletes, all with high potential; we just need to have faith in the process."
Attention now turns to next week's women's Olympic qualifier at the Laser Radial World Championship, which also take place in Sakaiminato.
It begins on Thursday, with Irish hopes pinned to Aoife Hopkins and Aisling Keller who can both secure a place for Ireland at the Tokyo Games.
