Thank you for your question and photos. It is virtually impossible to address your concerns without an examination. Possible causes of bulging above the belly button include excess intra-abdominal fat, a hernia, failure of the muscle plication sutures, a hematoma around the muscle, an encapsulated seroma, fat necrosis, or scar formation. A CT scan is not always helpful in getting a definitive answer. Exploration is sometime necessary if it bothers you. One question you need to address is whether this bothers you enough to undergo another surgical procedure with its attendant costs and recovery. It may not be worth it, depending on the problem. Discuss this matter further with your surgeon or another for a second opinion. Best wishes.
Looking at your photos seems that most of the bulge on your abdomen, comes from the intra abdominal content, like the intra abdominal fat, intestines, liver, etc. A revision on the muscle repair will not do too much, as, a tighter muscle does not decrease the volume inside the abdomen. What is effective is losing some weight and follow a regular routine of work out at least 3 times a week, for 30 minutes and you will see an improvement on the abdomen in few months.
I tell my patients that the muscle plication with a tummy tuck can loosen over time or the sutures can rupture. In addition, if you have excessive fat around your intestines, this will push out against the muscle and you won't have a flat stomach even after muscle tightening. Losing some of this fat with diet and exercise will improve how flat that you look.
To me over the internet opinion is you have to much visceral fat. Best to lose 30 pounds that you would see this bulge disappear...