Dell Vostro 3520 add a more SSD but have a problem

Hi everybody.

I have just add more SSD 240 Gb WD green to slot 2 of Vostro 3520, format as NTFS and GPT disk. I had a problem: Suddenly gone SSD ? If I restart or shutdown and turn it on, it will be appear and gone again. How to fix it ?

Sorry for my bad English.