FYI: In the past, I used TOS ThinkBack, OnDemand, and normal mode using ThinkScripts in search of usable (reliable) backtesting of options. I found that the quality and reliability of the information was varying, making it very frustrating to use, as I would put a good deal of effort then find the data would morph to something unusable. For example, currently (and for the last few years, OnDemand option pricing via the TOS GUI may not even allow visibility to near the money strikes (most of the time, only set of near the money were visible). ThinkBack is a quick and dirty tool for simple tests, but always had shortcomings that made it impractical for my normal backtesing needs. -- For ThinkScript, the threshold for "too complex" from TOS seems to be a moving target, so if you have something working today, the next update of TOS may not function at all. My observations for the last few months (an eternity in TOS time) is that RTD functionality in normal mode as well as in OnDemand has remained functional (except on weekends, OnDemand may cease to work for intervals, but is fairly easy to detect!).
Your screen grab implies that the issue is not so much with an N/A price, but that the expiration, strike, and everything for that OPRA is producing N/A! -- I have not observed this issue, but don't use ThinkBack much due to other issues with it. -- Unclear how reliable the price is from ThinkBack since it is only end of day values, and the bid/ask may change from market close until the values used by ThinkBack are captured (I do not think they clarify or guarantee this).
