Bitcoin Testnet Fee Estimation issues

Hi! Two questions/issues with Bitcoin Testnet fee estimation.

  1. When creating a transaction the initial fee value returns as “-1”. Does this happen when the fee estimation fails?
  2. When calling the fee estimation endpoint for Bitcoin testnet it always returns message='Error calculating transaction fee' code=1903

With the above two methods failing there is no way to see a fee estimate until the transaction is actually signed/broadcasting. Please let me know if there is something I am missing.