Chrome extension fails to install: CRX_REQUIRED_PROOF_MISSING

[Stephen-Hamilton-C]

Reporter Info

• Materia version: 20200320.0ubuntu1
• GTK3 version: 3.24.20
• Distribution (and version): Ubuntu 20.04.4 LTS
• Desktop environment (and version): GNOME 3.36.8
• Related application (and version): Google Chrome 101.0.4951.41

Actual Issue

Trying to install either the chrome-scrollbar.crx or chrome-theme.crx fails with the error message in the title.

Steps to Reproduce

1. Drag either chrome-toolbar.crx or chrome-theme.crx from /usr/share/themes/Materia/chrome/ into Google Chrome or Chromium as per README instructions
2. Get the error depicted in the screenshot

Additional Info

I have encountered this issue on two separate boxes. One running CentOS 7 with Chromium and Chrome, and this Ubuntu 20.04 box with Chromium and Chrome as well.
It doesn't matter which variant of Materia I use, none of the crx files will install and throw the same error.

[drainmachine]

Still happening