However, whilst Copenhagen were waiting for the Denmark international to sign his contract at a luxury hotel in the country, the player left the premises without warning and the deal collapsed.
The details are outlined in a report from La Voz de Galicia, which claims Sisto’s intentions were to instead join his former club Midtjylland, but they cannot afford his €5m buyout clause.
The result of all this means that he remains a Celta Vigo player and will return to the club’s pre-season ahead of La Liga restarting this month.
He is one of a number of players who has been told they are no longer part of Celta’s plans by boss Oscar Garcia, with David Juncá, David Costas, Jozabed Sánchez, Juan Hernández, Emre Mor and Uruguayan striker Gabriel “Toro” Fernández also set to depart this summer.
Sisto has fallen from prominence at Celta in recent times and made headlines for all the wrong reasons earlier this year, when he broke quarantine and returned to Scandinavia with his sister via a 3,000km car journey.
Born in Uganda to South Sudanese parents, Sisto moved to Denmark aged just two months and went on to prosper as a footballing talent within the nation.
The winger has won 21 caps for his nation but has not appeared for Denmark since 2018.
It remains unclear if Sisto will be remaining on Celta’s books next season or not, with the club actively trying to sell him.