Ok, but are you mining with their own miner or are you using XMrig? I try to enter on this pool: https://51pool.online/ but before enter there's an warning message on Chrome saying this site is not safe to enter If you can give more informations...
The reason for the warning is because of xmrig, variants of xmrig are used in various trojans to mine Monero has nothing to do with 51pool So Firefox and Chrome will tag it as unsafe.