Can a weak spot in my abdomen be causing a seroma to return almost seven months after lap. Ventral hernia surgery? If not than what could be causing the seroma to return?

Possible foreign bod. Occasionally if a material or patch was used and becomes colonized, it may be a cause of a seroma. This's hound be evaluated by your surgeon.
Recurrence. Could be a low grade infection, especially if you have a mesh, or a recurrence of the hernia. Okay to ask for culture of the fluid, imaging, ct scan, and consider a second opinion.