you're going to need to give read_excel more info in order to read your data in.
you can look at the documentation for read_excel by typing ?read_excel into your R console. You'll see the syntax for the function is:
read_excel(path, sheet = 1, col_names = TRUE, col_types = NULL, na = "", skip = 0)
so a data.frame in R can't have two header rows, so you should skip that first one. If that's row 1, then you could do:
read_excel("Coupon Receivable 04022019.xlsx", sheet= "Mapper", skip = 1)
see if that helps.