According to the official blog, ArchiveNode.io, the Ethereum mainnet archive node service, announced the end of the project because it believes that the service is no longer necessary and other alternatives already exist.
There is currently a strong market of remote procedure call (RPC) providers providing access to archived data, making this project obsolete.
It is reported that ArchiveNode.io has provided the service for free for developers, students and researchers for up to three years. An Ethereum Archive node is an instance of an Ethereum client configured to build an archive of all historical states.