Forse questo ti può aiutare:
(dalle faq di nanopool)
My hashrate on pool drops to zero and no more shares accepted, although miner is working as usual.
Most probably, DAG files on your miner were corrupted and it computes invalid shares. Try to stop the miner, delete DAG files and start the miner again.
DAG files location: %USERPROFILE%/AppData/Local/Ethash