Run
npm install
to setup.
And after that, change node_modules/@openzeppelin/contracts/token/ERC777/ERC777.sol
line33 to
IERC1820Registry constant internal _ERC1820_REGISTRY = IERC1820Registry(0x88887eD889e776bCBe2f0f9932EcFaBcDfCd1820);
Address of ERC1820 on Conflux is different from that of Ethereum.