Knitting ribbing in the round differs from on flat needles in that you do the same thing on each round, you don't k2, p2 and then p2, k2 as you would working flat. It's still the same knit the knits and purl the purls. If you're doing purl stitches you should see purl stitches in your work. I think the most common mistake is to try to work a round of k2, p2, then a round of p2, k2, which results in a different pattern. I wouldn't use the 2 straight needles method here. The gauge is different and I just don't think it would work as well. What video are you going by? Knowing which one might help in solving your problem. Another thing worh mentioning is that it can take several rows for the ribbed pattern to really show.