Neymar faces disciplinary action from Paris St Germain after failing to turn up for the first day of pre-season training.
The Brazil forward, 27, was scheduled to report back to the French club's training ground on Monday.
"PSG affirms that the player Neymar Jr was not present at the time and place required, without prior authorisation from the club," PSG said in a statement on their official website.
"PSG regrets this situation and will take appropriate action."
Neymar missed the Copa America tournament - which Brazil won by beating Peru 3-1 in Sunday's final - due to an ankle injury sustained in a friendly against Qatar last month.
He has been linked to a return to former club Barcelona, who sold him to PSG for a world-record transfer fee of £200million in the summer of 2017.
Neymar is banned for three matches at the start of the new Ligue 1 season after lashing out at a fan at the end of PSG's shock French Cup final defeat to Rennes in April.
The former Santos forward will also miss his next three European matches after insulting match officials at the end of his side's Champions League defeat to Manchester United in March.