From the SON regs
The U21 Rider must race in a minimum of 1 heat in each meeting, Final day 1 and Final day 2 will be classed as 2 meetings. If the U21 does not get nominated before the last programmed heat for his country he will automatically replace the rider in Red or White.
Macon club and French federation likely to be in hot water with FIM-EUROPE as they cannot run on the reserve date(today)- lack of medical cover i think is the reason given.