Indiegogo has said that it is willing to extend the deadline it gave to a project attempting to make a handheld version of a classic British computer.
But the crowdfunding site says that the team behind the ZX Spectrum Vega+ has yet to meet its conditions.
In February, Indiegogo threatened to appoint debt collectors if the campaign had not fulfilled its commitments by the end of May.
The project's chief told the BBC he was "still determined to deliver".
Dr David Levy added that he believed many backers "still are fully supportive of our finishing the project".
The campaign originally pledged to send out the console in the summer of 2016.
The company he chairs, Retro Computers Ltd (RCL), has issued an update to backers saying it now intends to deliver the first consoles by 15 June.
He also told the BBC that "Indiegogo has extended the date" to mid-June.
However, the US firm explained that the situation was more complicated.
"We've taken several steps to protect our community, including demanding refunds for any backer that has requested one and banning the campaign owners from launching any other project on our platform," explained a spokesman.
"We have also begun the process of sending the campaign owners to collections, which will commence unless the campaign delivers on the promises it made.
"More specifically, yesterday, we sent very clear requirements, which have not yet been agreed to by the campaign owners, despite them posting a campaign update earlier today."
The conditions required of RCL are that it:
- provide physical evidence of its readiness to deliver by sending a final unit to Indiegogo by 5 June
- give an immediate refund to any backer who has requested one and no longer wishes to receive the console
- provide contact details for a person at broadcaster Sky that is apparently delaying the consoles being sent out. The broadcaster owns some of the intellectual property involved
Indiegogo also disclosed that RCL had suggested it now planned to deliver the handheld consoles without 1,000 games pre-installed as originally promised.
"If these requirements are not agreed to... we will continue with the process of sending the project to collections, which has already begun, and we will immediately notify backers, as previously discussed," the Indiegogo spokesman added.
Sky has been asked for comment.
The Vega+ campaign raised a total of £512,790 from more than 4,700 people on Indiegogo before the US firm blocked it from accepting more funds in March 2017.
This was a highly unusual step for the fundraising service, which normally allows projects to decide when they want to stop accepting money.
According to RCL's most recently filed accounts, it had £433,008 of assets at the end of March 2017.
Should the company be forced to refund the cash, it would mark one of the highest-profile crowdfunding failures to date.
Its use of the iconic Sinclair brand has meant the project has been widely followed by both the gaming and mainstream press.
However, debt collection agencies lack the legal powers to force an immediate repayment.
What powers do debt collectors have?
While the involvement of a debt collection agency would escalate matters, it would not necessarily bring them to a close.
Unlike bailiffs, such agencies cannot seize assets themselves.
In past cases, some companies have simply opted to ignore them.
When this has happened, the agencies have sometimes had to pursue legal action on their clients' behalf.
And only when they won have enforcement officers been appointed with the power to confiscate property.
Bearing in mind that backers neither have a stake in RCL nor have they bought something in the traditional sense - rather they funded an endeavour - it is not clear how a judge would rule were Indiegogo to pursue this route, or even if the dispute would get to court in the first place.
"This is a complex and difficult case," commented Peter Wallwork, chief executive of the Credit Services Association.
He added that even when companies are forced to hand over funds, the effort required often involves "additional charges that would have to be met by the debtor business", eating into the sums recovered.
RCL has previously said problems with the console's hardware contributed to earlier delays.
But Dr Levy alleges that much of the blame falls on an ex-director of the firm, Paul Andrews, who he described as "the vilest enemy of RCL and the Vega+ project".
Mr Andrews told the BBC that he denied this and other claims that Mr Levy had made about him, which he said had "consistently proven to be false".
A recent dispute between the two men concerned the games that backers had been told would be pre-installed on the console.
On 22 May, RCL posted a Facebook update that accused Mr Andrews and others of casting doubt over whether it had the rights to supply the titles.
As a result, RCL said, it now needed to contact each rights-holder to confirm a licence had been granted, which would "take some time".
Mr Andrews has acknowledged that he had pressed the company to prove the devices were "fully legally compliant", but denied he was to blame for a delay.
"The RCL response was for them to write to all games rights owners... when already [many] games had been withdrawn by rights-owners," he told the BBC.
Mr Andrews is pursuing another avenue to bring matters to a head.
He and another ex-director, Chris Smith, each still own a 25% stake in RCL.
This has allowed them to force a shareholders meeting, which Mr Andrews said had been scheduled for 18 June.
They have proposed a motion that RCL's current management be removed and a "totally independent third party" take control.
"We believe it is the only way this ridiculous situation will be resolved for backers," Mr Andrews explained.
However, to succeed they need the support of Sir Clive Sinclair - the creator of the original ZX Spectrum. His firm, Sinclair Research, also owns a 25% stake in RCL.
Dr Levy - who owns the other 25% - noted that Sinclair Research issued a statement on 2 May that said it did not intend to replace RCL's directors.
But that commitment was based on an expectation that deliveries would take place last month, which did not transpire.
Sir Clive did not respond to a request to share his current view.