Why can I not find my transaction in the mempool?

Question

I built a native segwit raw v2 transaction with the pwpkh addresses, and get the decoded transaction as the follows

{
  "version": "02000000",
  "marker": "00",
  "flag": "01",
  "inputcount": "02",
  "inputs": [
    {
      "txid": "21f519154a6ea655dc07ca24dcb79f913185916e762616c474a5665411e3a273",
      "vout": "00000000",
      "scriptsigsize": "00",
      "scriptsig": "",
      "sequence": "fdffffff"
    },
    {
      "txid": "227514140e2e2d898216f30e7f6d48fd1d86df2f808e4c52f4c78cb179d29c9c",
      "vout": "00000000",
      "scriptsigsize": "00",
      "scriptsig": "",
      "sequence": "fdffffff"
    }
  ],
  "outputcount": "02",
  "outputs": [
    {
      "amount": "e803000000000000",
      "scriptpubkeysize": "16",
      "scriptpubkey": "0014abc97562daa3db9641b7d5e4eee7f756e8979b97"
    },
    {
      "amount": "fc46010000000000",
      "scriptpubkeysize": "16",
      "scriptpubkey": "00149dd4101feb1ced4060108728e35c0e42291854e9"
    }
  ],
  "witness": [
    {
      "stackitems": "02",
      "0": {
        "size": "48",
        "item": "30450221009a59d6bfe14a1a6dddf545dd1e5c625a9d40a1beaded6f5122ada82b2eb399fe022050b8964688d288557d74a5a1455770d458fbac970adb32d8fdafc132a744881501"
      },
      "1": {
        "size": "21",
        "item": "0294d85843f1fe213631c3c7338e868b3210e32da1bc41d83bfb1940d20bdb94a9"
      }
    },
    {
      "stackitems": "02",
      "0": {
        "size": "48",
        "item": "3045022100845c5d527a6b9ef719c865f5a5baa34e886efce65eb438c15259daaae756b76402203b49ea871db26b5f0b90387cfc5bd13835b84cfb2128d162780c432d68d7161101"
      },
      "1": {
        "size": "21",
        "item": "0294d85843f1fe213631c3c7338e868b3210e32da1bc41d83bfb1940d20bdb94a9"
      }
    }
  ],
  "locktime": "00000000"
}

I sent the transaction and it returned a txid,"faf1b468b3f25a8c48deff47be8ab969a638a9e4f3fd618b2d2f37d3f141b90b". I can not find it in the mempool or on Blockstream’s testnet block explorer, and I checked my transaction format again and again, but find no problems, so anyone can help me check this?

Answer 1

This transaction appears to not be eligible for confirmation because it spends inputs that do not exist.

You write that you are using testnet, but neither of the two transactions 21f5…a273 and 2275…9c9c that created the UTXOs your transaction is spending seem to exist on testnet. A transaction that spends unknown inputs is obviously not eligible for block inclusion and therefore will not propagate on the network. The absence of the parent transactions may be explained by you creating a long chain of transactions in excess of the default ancestor limits, the parent transactions were dropped from the mempool due to nodes increasing their dynamic minimum mempool feerate when it overflowed the memory limit, or an ancestor transaction being replaced by a conflicting transaction.