|Is this a desktop of laptop?|
Watch the POST screens that appear when you first start up the computer. You need to verify that the BIOS is properly identifying ALL the drives by BOTH the model and FULL capacity. If you don't SEE any POST screens then boot into the BIOS (setup) and disable fast start and any logos.
If the new drive is not identified at all then you may have the jumper on the back set wrong. Look at the old drive and set for the same setting. The position MAY not be the same though. Read the jumper positions on the label located on the top of the drive.
If the drive is identified by model but NOT the full capacity then post back for further instructions.