It’s possible you should actually be pursuing a promotion because the salary you requested is above the top of your current pay grade. Your manager may tell you this explicitly—”That raise would put you above the top of your pay grade”—or implicitly—“That would move you higher than most of your peers.” Either of these responses may mean that your best opportunity to keep things moving forward may be to pursue a promotion.
This can also happen when the market data you found doesn’t distinguish between levels of a position (Project Manager I, Project Manager II, etc.) in the same way as your company. Your research may indicate the midpoint for your job in your industry is $50,000, but maybe your company has split that job into two tiers—Junior and Senior. Moving up to $50,000 may move you above the top of the “Junior” pay grade, while it would leave you below the midpoint for the “Senior” pay grade. You may need to pursue a promotion to move yourself into a higher pay grade so that you have more room to increase your salary closer to the market midpoint.