Truffle flattener is not working on a smart contract which has @openzeppelin/contract3.4.0 version imported.

After running command npx truffle-flattener ./contracts/SimpleCollectible.sol > ./contracts/FlatSimpleCollectible.sol

I am getting an error
Error: ENOENT: no such file or directory, open 'c:/Users/Unity%20GG/Desktop/solidity/demo_py-solidity/nftdemo/node_modules/@openzeppelin/contracts/utils/Context.sol'
at Object.openSync (node:fs:585:3)
at Object.readFileSync (node:fs:453:35)
at resolve (C:\Users\Unity GG\Desktop\solidity\demo_py-solidity\nftdemo\node_modules\truffle-flattener\index.js:23:27)
at async dependenciesDfs (C:\Users\Unity GG\Desktop\solidity\demo_py-solidity\nftdemo\node_modules\truffle-flattener\index.js:62:20)
at async dependenciesDfs (C:\Users\Unity GG\Desktop\solidity\demo_py-solidity\nftdemo\node_modules\truffle-flattener\index.js:73:7)
at async dependenciesDfs (C:\Users\Unity GG\Desktop\solidity\demo_py-solidity\nftdemo\node_modules\truffle-flattener\index.js:73:7)
at async getSortedFilePaths (C:\Users\Unity GG\Desktop\solidity\demo_py-solidity\nftdemo\node_modules\truffle-flattener\index.js:83:5)
at async flatten (C:\Users\Unity GG\Desktop\solidity\demo_py-solidity\nftdemo\node_modules\truffle-flattener\index.js:188:23)
at async main (C:\Users\Unity GG\Desktop\solidity\demo_py-solidity\nftdemo\node_modules\truffle-flattener\index.js:245:3) {
errno: -4058,
syscall: 'open',
code: 'ENOENT',
path: 'c:/Users/Unity%20GG/Desktop/solidity/demo_py-solidity/nftdemo/node_modules/@openzeppelin/contracts/utils/Context.sol'
}

But context.sol file exit in the directory.

Truffle v5.5.20 (core: 5.5.20)
Ganache v7.2.0
Solidity - 0.6.6 (solc-js)
Node v16.14.2
Web3.js v1.7.4

Hello @Mazher_Hussain

This looks like the contract are not installed or at least not found. Make sure the dependency is set and installed properly.