ACR Failing to Load

"However, cannot open and Open tab is missing from CC Apps"

That is as expected. There is no (Open) icon for ACR in the CC Desktop App.

You cannot "Open" Adobe Camera Raw, instead you "Open" an image file in Photoshop, and if a raw file requires rendering to the Ps RGB format, it will open in ACR, before it opens in Ps.

ACR is a "Plugin" for Photoshop. Not an independent App.

You can, if you want,  'force' RGB rendered files (JPG, TIF) to go through ACR before appearing in Ps by a Camera Raw Preference setting in Ps .

And "Not Loading"- in what circumstances? File-type?