Canaan Inc, one of the world’s leading cryptocurrency mining equipment makers, has let its application for a Hong Kong IPO of at least $400 million lapse, casting doubt on the prospects for other Chinese makers of bitcoin mining gear.

Canaan’s application lapsed on Thursday six months after it was filed, the Hong Kong stock exchange’s website showed, amid optimism in the sector despite regulatory uncertainty and a slumping bitcoin price.

Hangzhou-based Canaan had been targeting at least $400 million – down from a figure of up to $2 billion touted earlier this year by people involved in the deal.

However sources close to the deal said the stock exchange and regulators had many questions about its business model and prospects.

The sources also said the IPO would not happen this year as there was no update from the stock exchange for a listing hearing.

Canaan could refile its IPO application with updated financial information if it planned to resume the process, the sources said.

Two other bitcoin equipment makers, Bitmain Technologies and Ebang, also have IPO applications pending with the Hong Kong stock exchange, though one direct source said Ebang’s listing would likely not take place this year either.

Bitmain is still in the process of answering questions from both the exchange and the Securities and Futures Commission (SFC), according to a separate source close to the deal.

Canaan and Bitmain declined to comment while Ebang did not immediately respond to a request for comment.

Canaan’s lapsed application comes two weeks after Hong Kong’s SFC said it would bring “virtual assets” such as cryptocurrencies further within its regulatory net.

The regulator said it would impose licensing conditions on firms which managed or intended to manage portfolios investing in virtual assets, irrespective of whether such assets constituted securities or futures, “in light of the significant risks virtual assets pose to investors.”

“Specifically because of the SFC’s announcement there will be quite a lot of changes in terms of the outlook of what they (crypto miners) can do,” said Stephen Chan, partner at law firm Dechert LLP.

The prospect of further regulatory action has weighed on the cryptocurrency sector, even as Canaan has sought to present itself to investors not so much as a bitcoin company, but as a chip designer focused on developing other markets in artificial intelligence and blockchain, the electronic ledger that underpins bitcoin.

The price of bitcoin dropped to a one-year low on Wednesday as a prolonged market slump that began at the beginning of the year weighed on crypto assets.

Bitcoin is now worth $5,543.76 compared to a peak of about $19,000 in December 2017.

A senior equity capital markets banker not involved in any of the bitcoin equipment makers’ IPOs said both the stock exchange and SFC had concerns over the companies’ business prospects.

“With the bitcoin price dropping so much this year, there’s a lot of uncertainties over their business. If we cannot forecast their financials, how can we sell their IPOs?” the person said.