The ex-wife of Donald Trump Jr, with whom she shares five children, announced in May that she had been diagnosed with breast cancer.
The country's populist right-wing leader of 12 years says it is "clear" his Serbian Progressive Party has lost.
Machado had left the country just a month before the US government seized Venezuelan President Nicolás Maduro.
Serbia is heading to the polls as a student movement attempts to oust longtime populist leader Aleksandar Vučić.
He will be observed to evaluate whether his "psychiatric health is compatible with pursuing his interrogation", authorities said.
The authorities had justified the ban by saying online content was fuelling conflict, while the opposition had condemned it as an abuse of power.
The International Weightlifting Federation becomes the first Olympic federation to choose Russia to host a world championships since its invasion of Ukraine.
Nayib Bukele says bodies delivered to soldiers are "not our men" amid search for Salvadorans abducted last week.
The tech billionaire accuses Ukraine of violating its terms of service by using the network for military activity.