i have an gtx 1070 which have 7.2MH/s and found only one block in 36 hours, 18 hours ago and an gtx 1980Ti with 6.5MH/s which didn't find any block on 36 hours of mining...
There is a problem with the 386.xx driver and 1080ti in the opensource miner (nonce not validated on the cpu)
Did you try to run the miner in benchmark mode?
downgrade to 382.xx driver.