Yes, this was my problem today when trying to submit a transaction - same error. Except in my case, my server was already processing the latest blocks.
For anyone who is using Cardano testnet and following these directions https://cardano-foundation.gitbook.io/stake-pool-course/stake-pool-guide/stake-pool-operations/transactions
where it says ‘submit transaction’, the instructions don’t work for my configuration.
Changing ‘export CARDANO_NODE_SOCKET_PATH=~/cardano-node/relay/db/node.socket’ to ‘export CARDANO_NODE_SOCKET_PATH=~/relay/db/node.socket’
will fix the problem. The highlighted part above in bold print is what gave me the same error.