I have 5v power adapter
What is the current rating for the power adapter? Pixels can get flaky when power is low and there is typically some voltage drop further down the strand.
Your connections are correct if the first pixels are working. As suggested, also check for broken wires - most common at the attachment to the pixels. Sometimes squeezing or wiggling the wires will bring them to life. Don't worry, we'll replace it if it is defective. Just trying to get an accurate diagnosis.