There was a version issue between the current installed version 1.4.0 and the local copy being using in the subfolder (/frontend-shared). The newest shared package exports an _index.scss file which is required by the client, but it was not formally importing a version of the shared package which exported the _index.scss file. The client now imports 1.9.0 which has _index.scss and now the frontend-shared folder can be fully removed from the client.

TL;DR, This is just more reason to move the shared package to its own repo because this issue was being masked.