I may not be doing something correctly then.
Here is what I have done.
Created an account.
Created a "buy" transaction with a fictional ticker (since it is not public,) let's say XXYY. So, for example, it is buy 5000 shares of XXYY at $2 per share.
In Stock Data, then, that information propagates itself every day. In this example, 5000 shares with a value of $10000, under ticker XXYY.
When I hit Add Data, the New Data window opens. There are 3 options for Type - price, dividends, and split. I select Price.
The problem occurs with the Position pull down selection. The ticker XXYY is not present as an option. The other tickers (valid, tradeable tickers) from other accounts are present, however.
I hope this is enough information to identify the situation, please let me know if I can add anything.