I know that it's my problem, but I don't have any idea what happened.
Early on, all was good. A few days before the hard fork, I upgraded the monero cli tools to the latest version, and they had been working fine before the night from 15 to 16.
I've not found anything in the monerod logs (from time to time i'm getting INFO stacktrace src/common/stack_trace.cpp:120 Exception: cryptonote::BLOCK_DNE but it's started much early with upgrade to version v0.11.0.0)
(and I just checked, it's still here).
Version of monerod is ./monerod --version Monero 'Helium Hydra' (v0.11.0.0-release)
So, I don't have question.. I just don't realize what happened, I have not changed anything on the pool server, my miners all are here and working fine and getting updates from the pool ..
I really need any advice.. Thanks!