From @nanopool_org twitter:
Some of our Ethereum nodes got into fork. We are working to restore the blockchains on the nodes and fix the problem. Balances and payments will be recalculated and pool downtime compensated in next few hours.
7:26 PM · Dec 8, 2019
Yeap, so it's Nanopool fault or just maintance. It was mining again for a while, almost stable again but now it can't even connect but I guess we just have to wait. Doesn't matter now is it with "-allcoins 1 -allpools 1" or without. BTW I've chcecked that pings to Nanopool are around 45ms, to Ethermine 35ms so will switch to them after next payout. At least to try.
O-ho! It's connecting again!