Upfront - not a lot of information - based on what I read I assume that this is an internal installation. If that is the situation, my first guess is that you may have a connector that is not seated. Murmur, murmur; hope you still have the case open - - -
Is there an installation disk that came with the drive? If so, have you done that install? Is your machine able to address and use an SSD? I would think so, then maybe not!
If you have walked these paths, are you able to verify that the drive itself is operational? DOAs are rare today, they do occur in the best of families. If you can verify the drive elsewhere - it would be good.
There is always the Dell and the Seagate support channel. I would make the first pass at Dell and ascertain that the machine is able to utilize the drive. Are there any steps needed to help it along? With that resolved - what does Seagate support?