My Book changed permissions

I have been moving files to a 8TB My Book connected wirelessly via my modem/router that it’s connected to via USB. Until recently, no concerns with this, however it has just decided to prevent me from doing this, telling me I now no longer have permission to edit the volume (see attachment). I have full admin access on my computer, so now I’m really not sure what to do.

Screen Shot 2020-04-12 at 8.16.19 pm