Us 1 a function-definition is not allowed here before '{' token

If anyone might have a clue why this is happening, I’d really appreciate the assistance. I knew there was bound to be compiler errors, but I have no clue why this is unacceptable.
Unfortunately, I can’t post the entire code, there’s some proprietary bits in there I can’t show.
In short, the function’s purpose is to write “H2O?” to a virtual pin using the Blynk library, to which a slave device will respond by uploading two data points that the function pulls down from the virtual pin.

BLYNK_WRITEvPin() is a function all on it’s own… not to be included inside another function or void().

Instead you would call that function with a Blynk.syncVirtual(vPin) command with the vPin being the same one of that BLYNK_WRITE(vPin) function.