When opening Authoring in Cognos 11.1.7 (GA or IF1) in Chrome 85, the following error appears:
TypeError: Cannot read property 'cssRules' of null at Object._enn._60g
It turns out that Chrome 85 does not work with these versions of Cognos due to changes within Chrome. The issue is documented in APAR PH29011. Note that the new Chrome-based Edge browser version 85 would also experience this issue.
Thankfully, IBM released Cognos 11.1.7 IF2 on or about September 11, 2020. This interim fix resolves the issue and allows current Chrome browsers to open Authoring.