Fail with error 'TransferHelper: TRANSFER_FROM_FAILED'

Question

I'm trying to create a script to sell token on pancakeswap and cant seem to get it to work.

I'm able to buy just fine but cannot sell.

I'm getting Fail with error 'TransferHelper: TRANSFER_FROM_FAILED'

The script is a hit and miss with the balance of the tokens depending of the decimals. I just wish there was a way that I could put 100% of balance.

    pancakeswap2_txn = contract.functions.swapExactTokensForETHSupportingFeeOnTransferTokens(
      tokenValue, 0, [contract_id, spend],
      sender_address,
      (int(time.time()) + 1000000)

    ).buildTransaction({
      'from': sender_address,
      'gas': 1800000,
      'gasPrice': web3.toWei(input("How much Gwei: "), 'gwei'),
      'nonce': web3.eth.get_transaction_count(sender_address),
    })

    signed_txn = web3.eth.account.sign_transaction(pancakeswap2_txn, private_key = config.private)
    tx_token = web3.eth.send_raw_transaction(signed_txn.rawTransaction)