Multi-variable Solver Issue

I'm trying to optimize (via Solver) a fairly elaborate financial model. Here are the basics:

- Changing cells are two rows of variables (one row is how much capital should be debt the second is how much capital should be equity).

- I have set constraints on the changing cells, so that the choices are pre-determined amounts to use (anything from $10M to $100M)

- Now let's say that there are 4 columns (representing 4 financial quarters): i.e. there are 8 changing cells (4 in each row for debt and equity).

- For each quarter (column) a certain ratio is calculated depending on the mix of debt and equity Solver chooses. My target cell simply takes the average of that ratio across the 4 quarters and minimizes it.

This may be where my problem arises. The ratio calculation per quarter is dependant upon the amount input for debt and equity, but is somewhere from 3-5 calculations/formulas removed from that initial input. Meaning that what is input into either a debt or equity cell rolls into one formula, that output rolls into another formula, that output into another, and then that output into the ratio formula. So they are all connected in the model, but it's not an immediate connection between debt/equity to the ratio calc.

Solver cannot find a solution for me and I think it's because there are several layers between the changing cells and my target cell. Can anyone tell me if that may be my issue here or if I should look at something else.

Thanks.