From: South Carolina
I figured out the production problem and it's pretty ugly.
Looking at the database I noticed that all Japanese planes have their engine types in weapon slot #10. Allied planes have nothing in weapon slot #10, because the Allied production model is abstracted - they don't explicitly require engines.
However - those Allied planes that are not producing do have something defined in weapon slot #10, namely a radar.
As a test I modified the Anson I. You will recall I have verified that the Anson I is not producing in my game even though it has 30 factories. I modified the record for the Anson I to zero out weapon slot #10. Then I ran a test - and the Anson I started production on the very first day.
By the way, in the game I have running (where the Anson I has a radar defined in weapon slot #10), the radar does not show up on the aircraft details display.
There are many Allied aircraft with weapon #10 defined as radar, but because I am early in the game (now May '42) only those few types I noticed and mentioned are yet supposed to be producing, but of course are not. No Allied planes with a weapon #10 defined (as other than zeroed out) will ever be manufactured.
I suppose the radars have to be moved to a different weapon slot.
I just did a test by putting the start date to June 45 and confirmed this. There is no production that I can see for any aricraft with a radar in slot 10. (As a side note slot 156 PBN/PBY/GST is producing and the radar is in slot 9)
using AIO 7.788
Did a second test (June 45) this time with slot 10 radars cleared, I'm now getting production on the aircraft.
witpqs is correct, the radars will need to be moved.