Hi Diya,
I found this in your input file:
awk '$2==11{print}' eGFR_CKDGEN_UKBB_MVP_EUR_noMHC_b37_FUMA_final.txt | grep NA
rs34287067 11 47757631 NA NA 0.0000000000 0.0021157900 0.008491 223386
While for the other rows:
head -n 3 eGFR_CKDGEN_UKBB_MVP_EUR_noMHC_b37_FUMA_final.txt
SNP CHR BP A1 A2 BETA SE P N
rs17244250 9 139818770 C G 0.0002449400 0.0010983800 0.8239 828879
rs7860304 9 139819398 C T 0.0009126940 0.0010826700 0.3994 853109
You can either remove the problematic row (or rows - you need to double-check) or fill in the alleles for the missing ones.
Best,
Tanya