In your project's root directory, there is an Anchor.toml file.
Within that file, there is a [provider] section.
[provider]
cluster = "devnet"
wallet = "~/.config/solana/id.json"
The cluster = "xyz" line needs to point to the same cluster that you are trying to deploy to.
There are four possible values: localnet, devnet, testnet and mainnet.
So when trying to deploy to devnet, make sure you have cluster = "devnet" in the [provider] section of your Anchor.toml.