Hi @diffracteD,
Unfortunately we do not have a way to resume 2D Classification or Refinement jobs that failed in cryoSPARC, at the moment. However, this is possible in cryoSPARC Live (https://cryosparc.com/docs/live). We hope to add similar functionality into cryoSPARC soon.
If you are okay to start from raw movies, you can import these into cryoSPARC Live, have the cryoSPARC Live GPU workers take care of preprocessing (motion correction, ctf estimation, picking, extraction), and then use the Streaming 2D Classification job in Live, which if it fails, will be able to continue from a last saved state.