Seems like the OpenWRT images for Globalscale Espressobin V7 posted on this page got corrupt at the time someone packaged them. I'm unable to extract them using 7-zip on Windows or on Mac, same error. Both Install and Upgrade files are corrupt, so all 4 files.
Can someone please re-up the proper image files which are not corrupt?
Thank you very much. That explains it. I used Winzip and it extracted it without any errors and now the Espressobin is booting using this image as it should