RVN Hashrates dropping to 0 after about 30 mimutes

Hello fellow miners,

I am new to mining and i recently downloaded MBminer to mine RVN on 2miners pool

however, my pool hashrates keep dropping to 0 after just about 30 minutes of mining. (pool hashrates 10m:0 and then 1h and 24h drop down to 0 graduaply after that)

what can be the problem? any help will be highly appreciated!