Potential bug - SAM does not seem iterating IRR

I am getting some very strange results for IRR and NPV in this SAM file (attached). I am running an IRR target analysis (15%) but it seems that SAM is not performing any iterations. It is reporting an internal return of 70+% and an NPV of $1 billion. Also, altering the incentive structure (e.g., PTC, ITC, none) seems to have no impact on PPA price output.
The 390 MW offshore wind project you are modeling generates about 1,500 million kWh annually, and has a total installed cost of about $2.2 billion at $5,600/kW. You assumed a 70% debt fraction (Independent Power Producer financial model), so the Year 0 net cash flow is about $670 million. Here's what the net after-tax cash flow looks like:

This graph shows a few things: The effect of the 30% production tax credit (PTC) in Year 1, and the accelerated depreciation (5-year MACRS) in Years 1-5. You can also see that the cash flow is positive for all years, and that the loan payments end in Year 15 of the 20-year project. The graph is a useful tool for a first-order evaluation of your results.
You specified a 15% target IRR, and as you observed, SAM calculated a PPA price of 24 cents/kWh with an internal rate of 70% (much higher than the target), and a very high net present value of $1.1 billion. Those unrealistic numbers usually indicate that your assumptions may be unrealistic.
Here are some things to try:
1. Try specifying a PPA price to see what IRR SAM calculates for the same set of assumptions. I ran parametric simulations over a range of PPA prices and found that the NPV switches from negative to positive somewhere around 11 cents/kWh with an IRR of around 24% (still a little high):

2. Try adjusting the debt fraction. It affects both the Year 0 and out-year cash flows. Because SAM assumes that debt interest payments are tax deductible, increasing the debt fraction while holding other assumptions constant typically increases the internal rate of return. Here are the results of  parametric simulations on debt fraction with a target IRR of 15%, which suggest that your assumption of 70% is driving the IRR and NPV to unrealistically high values:

3. Try loosening the constrainnts on the IRR by clearing one or both of the Constraint: Require a minimum DSCR and Constraint: Require a positive cash flow check boxes on the financing page.
After that evaluation, I decided to use a debt fraction of 45%, and to remove the positive cash flow constraint. With all of the other assumptions as they were in your original analysis, that gave me an IRR of 15% (equal to the target), and a net present value of $277 million, which seems more reasonable than the original $1.1 billion. The cash flow also looks reasonable:

Best regards,

Paul.