I am having problems with reading in .ped files using snpsStats::read.pedfile.

I try to read in the pedfile into R:

>sampleA <- snpStats::read.pedfile(file = "sampleA.ped", snps = "sampleA.map")

I used this before on a different pedfile and was able to identify the SNPs (snp.names) by RS#, however, now I receive the following error:

Error in snpStats::read.pedfile(file = "sampleA.ped", snps = "sampleA.map") :    
No unambiguous snp names found on file

If I just read it in with

>sampleA <- snpStats::read.pedfile(file = "sampleA.ped")
>head(sampleA$map)

I get:

snp.name allele.1 allele.2
locus.1  locus.1        G     <NA>
locus.2  locus.2        G     <NA>
locus.3  locus.3        C        T
locus.4  locus.4        A     <NA>
locus.5  locus.5    CCCCT        C
locus.6  locus.6        G        T

Which doesn't identify the snp.names as RS #'s.

Does anyone have any suggestions on how to fix this?