Since you have not shown any data, I am guessing at the cause of your problem. The variable d seems to be a data frame, since you use it in ggplot(). The function ma(), which comes from the package forecast, takes a univariate time series as its first argument. Here is a quote from the documentation.
ma {forecast} R Documentation
Moving-average smoothing
Description
macomputes a simple moving average smoother of a given time series.Usage
ma(x, order, centre = TRUE)
Arguments
xUnivariate time series orderOrder of moving average smoother centreIf TRUE, then the moving average is centred for even orders.
I would expect ma() to throw an error if you pass it a data frame (edit: if it has more than one column). If my answer has not helped you solve your problem, please tells us what d is and what error your are getting. The best way to post is question is with a Reproducible Example.