I try to verify a contract which doesn't have any constructor arguments, but I get an error:

npx hardhat verify --network harmonyMain 0x12f9c4b725457c48a3aD761530D8a7e5282E57E7 --contract contracts/OneUsdOracleMainnet.sol:OneUsdOracleMainnet
Error in plugin @nomiclabs/hardhat-etherscan: The contract verification failed.
Reason: Fail - Unable to verify
Is there someone who can help?