The district attorney's office said they are unable to move forward with criminal charges and are placing the investigation into an "inactive status."
"The investigative team determined that, based on the current state of the evidence, we cannot prove beyond a reasonable doubt that a crime was committed," the DA's office said in a statement.
Greenberg was 27 years old when she was found dead of more than 20 stab wounds inside her locked Manayunk apartment in 2011.
She was discovered by her fiancé on January 26, 2011, at the Venice Lofts on the 4600 block of Flat Rock Road.
Ellen's fiance has never been suspected by authorities of foul play.
Greenberg's family has long sought to get her suicide ruling changed to homicide or undetermined, have filed two lawsuits against the city.
The Philadelphia Police Department, as well as the Philadelphia District Attorney's Office, investigated the case, which was initially ruled as a homicide after an autopsy. That initial determination was later changed to a suicide by the Philadelphia Medical Examiner's Office.
Then, in 2018, the investigation was turned over to the Pennsylvania Attorney General's Office for review since Philadelphia District Attorney Larry Krasner had previously represented the Greenbergs.
The attorney general's office agreed with the suicide determination. But in July 2022, the AG's office, due to an "appearance of a conflict," kicked the case back to Philadelphia. The case was then handed to Chester County.
Since then, Chester County investigators say they have been working to determine if there is sufficient evidence to reopen the investigation.
On Friday, those investigators revealed that their team has determined that they cannot prove "beyond a reasonable doubt" that a crime was committed, adding that without this standard of proof, they are placing the investigation in an "inactive status."
Officials added that there is no statute of limitations for criminal homicide in Pennsylvania.
"Because investigation can take new directions, we are not closing the case," Chester County District Attorney's Office said in a press release.