Why are you not getting more traffic after raising your bid? Well, bid is not the only thing that determines your win rate (deliveries/ opportunities). Let's look at all of the determining factors when it comes to which ads get shown and your won rate.
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It may not be the only factor but it is definitely the biggest. It is important to note that simply increasing the bid won't directly mean more traffic. There might be large gaps in-between your bid and the next best one. This could cause a stagnation in won rate even after a sizeable increase in your bid. Conversely, a wise affiliate knows to continuously check the gap under their ad by occasionally reducing bid to make sure they are in the position they should be. Ideally, you want your win rate to be around 40%.
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The click-through rate is the other half of the equation in your overall add rank. Ads are chosen not only by the bid amount but also by the likeliness that someone will click on your ad. This is how ads with lower bids can outrank ads with higher bids. Increasing your CTR is a great way to increase your overall ad rank so you can spend less money.
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The different types of traffic can have a huge difference in avg CPC. This is because some traffic has, on average, better results than others. This is easily seen in the differences in traffic from different devices. The CPC for tablets could be above $0.060 while the CPC for smartphones could be $0.050. If you were bidding on both tablet and smartphone traffic, you may be winning 50% of the traffic with a CPC bid of $0.052 but you wouldn’t see a change in your win rate if you only raised it $0.005. On the other hand, if you deceased your bid by $0.005 you would lose most of your traffic. As you can see these gaps can create situations that make it hard for a simple increase in your bid to directly correlate to a linear increase in traffic. 

Another example is User Freshness. Because new (fresh) users are normally more likely to click and buy from an ad, they are often a more expensive traffic group. There are various other notable differences between sources (time, area, carrier, network). These gaps could again make it difficult to increase traffic by increasing the bid. You may be winning 95% of the cheaper traffic that only makes up 50% but maybe the next 30% of traffic has double the average CPC than that of the first 50%. A general rule of them is the more specific your campaign is, the easier it is to match your bid to the average bid of that traffic.