Osmar package in R "Error in file(con, "r") : cannot open the connection"

I am trying to run the osmar package on my windows 10, R 3.4.2, and have correctly installed osmosis. However when I try to run the code:

>library("osmar")
>
>src <- osmsource_osmosis(file = "c:/users/ben_c/Documents/FYP/FYP_NL_Map/muenchen.osm", osmosis = "osmosis")
>
>
>nl_bbox <- center_bbox(11.575278, 48.137222, 3000, 3000)
>
>nl <- get_osm(nl_bbox, src)
>
>plot(nl)

I get the warning, after osmosis has run:

>Error in file(con, "r") : cannot open the connection
>In addition: Warning message:
>In file(con, "r") :
>  cannot open file 
>'C:\Users\ben_c\AppData\Local\Temp\Rtmp8YYPkZ\file1b182fca7802': No such file or directory

I also get the same error when I run the demo:

>demo("navigator")

I am relatively new to R so would really appreciate any help.

Thanks in advance,

Ben