Monero-GUI solo mining

 To fix the Monero GUI "couldn't start mining" error in solo mode, ensure your local node is fully synced and use --start-mining <wallet_address or --start-mining <wallet_address> --mining-threads <number in the Daemon startup flags under Settings > Node. Solo mining requires a local node, unlike P2Pool. 

Troubleshooting Steps

Verify Synchronization: The "Local node" status must be "Synchronized".

Run as Admin/Root: Ensure the GUI has permissions to start the daemon (monerod) and utilize high-performance CPU settings.

Check Node Settings: In Settings -> Node, ensure you are using a local node (127.0.0.1:18081) rather than a remote one, as solo mining demands a fully synchronized local blockchain. 

Startup Flags for Solo Mining 

Enter these in Settings > Node > Daemon startup flags: 

--start-mining <Your_Wallet_Address>: Automatically starts mining when the daemon starts.

--mining-threads <N>: Sets the number of CPU threads (e.g., --mining-threads 4).

--bg-mining-enable: Enables background mining, allowing the node to mine while you use the computer. 

Example Configuration

To solo mine with 4 threads using your address:

--start-mining 48...your_address... --mining-threads 4 --bg-mining-enable 

Note: P2Pool is recommended over solo mining for most users because it allows for more frequent payouts while maintaining decentralization, explains the Monero/P2Pool website.