readSDMX to data.frame results in NULL?

Question

I can't seem to get my rsdmx results to convert into a data frame. All the help tutorials I can find parrot the same thing, but when I try it I get a NULL df. There's data coming from my readSDMX, but as.data.frame results in NULL.

What am I missing??? Is there something about this ASB dataset?

library(rsdmx)

sdmx2 <- readSDMX(providerId = "ABS", resource = "data", 
flowRef = "ABS_ANNUAL_ERP_ASGS2016",
key = list("ERP", "SA2", NULL), start = 2006, end = 2016, dsd = TRUE)

df <- as.data.frame(sdmx2, labels = TRUE)

head(df)

Thanks.