I'm trying to deploy a Smart Contract on Polygon mainnet but this happens when I run the migrate command using truffle

> Network name:    'matic'
> Network id:      137
> Block gas limit: 30176202 (0x1cc73ca)


1_initial_migration.js
======================

   Deploying 'Animals'
   -------------------
 *** Deployment Failed ***

"Animals" -- transaction underpriced.


Exiting: Review successful transactions manually by checking the transaction hashes above on Etherscan.


Error:  *** Deployment Failed ***

"Animals" -- transaction underpriced.

    at /Users/nick/node_modules/truffle/build/webpack:/packages/deployer/src/deployment.js:379:1
    at runMicrotasks (<anonymous>)
    at processTicksAndRejections (node:internal/process/task_queues:96:5)
    at Migration._deploy (/Users/nick/node_modules/truffle/build/webpack:/packages/migrate/Migration.js:68:1)
    at Migration._load (/Users/nick/node_modules/truffle/build/webpack:/packages/migrate/Migration.js:54:1)
    at Migration.run (/Users/nick/node_modules/truffle/build/webpack:/packages/migrate/Migration.js:202:1)
    at Object.runMigrations (/Users/nick/node_modules/truffle/build/webpack:/packages/migrate/index.js:152:1)
    at Object.runFrom (/Users/nick/node_modules/truffle/build/webpack:/packages/migrate/index.js:117:1)
    at Object.runAll (/Users/nick/node_modules/truffle/build/webpack:/packages/migrate/index.js:121:1)
    at Object.run (/Users/nick/node_modules/truffle/build/webpack:/packages/migrate/index.js:86:1)
    at runMigrations (/Users/nick/node_modules/truffle/build/webpack:/packages/core/lib/commands/migrate/run.js:78:1)
    at Object.module.exports [as run] (/Users/nick/node_modules/truffle/build/webpack:/packages/core/lib/commands/migrate/run.js:44:1)
    at Command.run (/Users/nick/node_modules/truffle/build/webpack:/packages/core/lib/command.js:189:1)
Truffle v5.5.1 (core: 5.5.1)

This is my truffle-config.js

matic: {
        provider: () => new HDWalletProvider(mnemonic, `https://polygon-mainnet.g.alchemy.com/v2/key`),
        network_id: 137,
        confirmations: 2,
        timeoutBlocks: 200,
        skipDryRun: true
      },

Does anyone know why is this happening?