The message "An athlete is not registered, the related result will be flagged as "not registered" and won't count in any ranking" appears if the concerning athlete is not correctly registrated by the National Federation.

Probably causes:
A. The athlete has been entered manualy and the FEI ID is not correct.
                         ==> Enter the correct athlete FEI ID
B. The registration for the current year has not been done. (Check the rirder in the FEI database)
                        ==> The athlete or PR needs to contact the NF the have the registration completed.