Help Igrf mgd77magref urgent

Hello, I am new to GMT and I am trying to calculate the Igrf using mgd77magref,
i’ve been through the documentation and my syntax seems correct, but gmt returns an Error sayin my data file (inputfile) is empty.
i have tried (.m77t / .csv/ .xlsx ) formats but the i got the same result.
this is the command line
gmt mgd77magref igrf.m77t -A+a10 # or .csv or .xlsx
Any help is welcomed. thanks

Here it seems to work as expected:

$ > igrf.m77t # make an empty file
$ gmt mgd77magref igrf.m77t -A+a10
mgd77magref [WARNING]: File igrf.m77t is empty!
mgd77magref [ERROR]: Input data have 0 column(s) but at least 3 are needed
$ echo -45 -23 2020-10-11T00:00:00 > igrf.m77t # make an input file
$ gmt mgd77magref igrf.m77t -A+a10 -Frthxyzdi/0
-45 -23 2020-10-11T00:00:00 22950.4191959 17643.0916056 16334.7486352 -6667.43342138 -14677.978739 -22.2040470369 -39.7583961792

take a look in
to see how to use -Fflags