to cover the costs of their legal campaign.
"We can see the contents of our Ethereum wallet, which is currently valued at more than $5.9 million," they said.
"Unfortunately, we have no means to access the coins in our wallet in spite of having the CoinBase time-stamped receipt and character password, notwithstanding all the other efforts we have put in."
LEGAL BATTLE The couple claim the Ethereum Foundation was supposed to send over the JSON file - which would have given them access to the wallet - but the files "refused to respond" as they were meant to.
"Ethereum reassured us that they had a backup wallet file which they would email to us," they said.
"Unfortunately, no one from their end followed up... and the email never came through."
Yuki and Art said it has become harder to reach the Ethereum Foundation "as the project became successful and attracted millions of cryptocurrency enthusiasts".
The couple have now begged for help to raise $250,000 to take their legal fight to the International Chamber Of Commerce.
"The last few years have been utterly challenging for our family," they said.
"My family and I have been through a lot. Just a few years ago, we lost everything we had to a house fire and had been on a long path to recovery since then.
"We are in dire need of some stability and still want to do a lot more for our community's less privileged people."
Speaking to , Art said: "All they have to do is send me that JSON file."
But the Ethereum Foundation's legal team reportedly said: "We continue to believe that Ethereum has no liability for lost wallets, passwords, and private key."
Art Williams and his wife have been battling to get the correct file to access the wallet Credit: wjla.com The couple bought 3,000 Ethereum coins Credit: wjla.com
Utah man lost £278k in cryptocurrency scam after being tricked by fake trading app