1099 R form does not have distribution code in box 7. what should I select?

[MichaelL1]

You need to go back to who issued the 1099R as it is not complete if there is no code in Box 7.

The most common code is actually a "7" normal distribution.  

Call the issuer on Monday and see what you can find out.  If they will give you the code over the phone, you could file while they issue you a corrected 1099R.