As an update in the event anyone else has this issue, it appears that uninstalling and re-installing worked for me. I started two different basic fictional leagues and trading did occur. However, the trading didn't start until 5/27 with trading frequency on very high and 6/23 with trade frequency on average. Both leagues started around 4/1. That could just be coincidence though.
Neither league started with inaugural drafts so maybe the distribution of players was good enough that trades were not needed. So I guess, I'll just move forward and assume I just had a problem with my installation.
