NAs in assoc file

[lubapardo]

I am getting a lot of NAs when running single test rvtest using score method. I can understand that for rare variation the association will fail but I also have SNPs that are common and still the association analysis did not work. Is there anywhere where I can find are the reasons for the NAs in the ouput assoc files?
regards,
chr22.dose.vcf.gz" --out "outfile" --covar "phenocov _ --covar-name "age ,sex,C1,C2,C3,C4" --pheno "pheno.txt" --dosage "DS" --single "score" --freqLower 0.010000 --hide-covar

Luba Pardo