Orbo update file faulty RBS40V-V2.3.0.10

> [...] after unzipping the file [...]

   Your attached picture shows what's in the zip archive; it does not
show that you've extracted the file(s) from the archive.  Which you'd
need to do before you could load the ".chk" file into the router.

> [...] contained in the zip it is not the correct format, [...]

   Says who?  Some zip/unzip program or other?

> [...] so the update will fail whichever method you choose auto or
> manual.

   Says who?  Did you try it?  How exactly?

      https://community.netgear.com/t5/x/x/m-p/1724099

> Try changing the name from *.chk to *.img.

   That sounds to me like a seriously poor idea.  Have you ever actually
tried it?  On anything?