etclabscore/cpp-etchash can not search solution by search_light

[caiqinghua]

int epoch_number = block_number / 30000;
const struct ethash_epoch_context *context = ethash_get_global_epoch_context(epoch_number);
ethash::search_result ethash_result = ethash::search_light(*context, header_hash, boundary, nonce, 1);
if (!ethash_result.solution_found) {
return LOW_DIFFICULTY;
}

The code can search solution for ethereum, but can not for etc node and cpp-etchash code. Please help me
@q9f @iquidus