Unknown error Transaction expired

I installed aptos-cli.
And then, I executed this command: aptos init
But the result is like the following:

Configuring for profile default
Choose network from [devnet, testnet, mainnet, local, custom | defaults to devnet]

No network given, using devnet...
Enter your private key as a hex literal (0x...) [Current: None | No input: Generate new key (or keep one if present)]

No key given, generating key...
Account 3a951caf0b18108c753eecd561b0d71ec45b61b8146457fe4036880545dfbdb0 doesn't exist, creating it and funding it with 100000000 Octas
  "Error": "API error: Unknown error Transaction expired, without being seen in mempool. It is guaranteed it will not be committed on chain."

What’s the problem?
Please help me.