Double check you pool address. I had the same issue last night when I freshly compiled XMR-STAK and pasted "pool" from some old release (2.2.0) where I had address wrong.
I chatted with admin @fairpool and he helped me out to find issue with pool address.

mine.sumo.fairpool.xyz:5555

Try it.
Make sure you use the newest xmr-stak and you select sumokoin as algo to mine.


From my webui for 1 vega


Difficulty   19195
Good results   2430 / 2430 (100.0 %)
Avg result time   14.4 sec
Pool-side hashes   46941923

Pool address   mine.sumo.fairpool.xyz:5555
Connected since   2018-04-05 01:13:45
Pool ping time   183 ms

Ping not the greatest but 100% so far.