The signature of the user operation was rejected or ran out of gas. "OOG" is an abbreviation for Out-Of-Gas.

There are two causes:

1. Signature verification ran out of gas
2. Signature verification has an error

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Solutions

1. Check the account has ETH to pay for its creation if you aren't using a paymaster.
2. If you are using a paymaster, verify the paymaster is set.
3. Investigate why the initCode used more gas than expected using tools like userop.dev, Tenderly, or the ERC-4337 Devnet.
4. Reach out to your bundler provider or ask a question in the Stackup Discord server for help. Be sure to include the user operation and any relevant information about how you're building it.