Why did Cuba insist on attending the Summit of the Americas?

Since Fidel Castro stepped down, Cuba experienced some political reforms that potentially explain why Cuba has more interest in cooperating than in previous summit years.
Belated Half Measures on Cuba

My time as a U.S. diplomat in Cuba during the Obama thaw of 2015-17 showed me what was possible to achieve when diplomacy was given a chance to work.
Daniel Ortega Begins His Fourth Consecutive Term

Last Monday, Daniel Ortega was sworn in for a fourth consecutive term as president of Nicaragua.
Why Cuba’s Díaz-Canel Is Still in Trouble
Historic wave of protests washes across Cuba

This past Sunday, the largest popular protests in decades erupted in Cuba, with thousands of demonstrators across the island taking to the streets to decry acute shortages of basic necessities (including food and medicine), rolling blackouts, and suffocating restrictions on political freedoms that persist over six decades after the Cuban Revolution.
How should the U.S. support change in Cuba? Lift the embargo.

It’s time to call the Cuban government’s bluff. Ending the embargo would help the country’s embattled private sector, giving its people hope for a non-Communist future.
A dubious referendum on a (slightly) revised constitution shows growing opposition to the revolution in Cuba
Even with likely fraud, the number of no votes, null votes and blank votes exceeded one million on Sunday’s referendum.
Cuba Wars Redux
A cancelled State Department panel on Cuba offers a teachable moment for the U.S. government. The Trump Administration should re-establish appropriate boundaries between politics, policy and intelligence on matters of Cuba.
Now what, Cuba?
Havana’s continued restrictions on the private sector (not to mention its ongoing suppression of fundamental political rights and civil liberties) present the greatest obstacle to entrepreneurial success on the island.
What Is Cuba’s Post-Castro Future?
Miguel Diaz-Canel, set to replace Raul Castro as president of Cuba after sixty years of Castro rule, will be faced with the challenges of implementing economic reform and sidestepping regional isolation.