OK.  For everyone's benefit who is still experiencing the problem of adding time trackers, I ended up emailing the CEO of Intuit.  He put me in touch with Andrea in the Office of the President to diagnose and fix the problem.  She immediately recognized the problem as something they internally call a "broken user" problem.  Basically, the log in credentials for an email become corrupted multiple times.  Andrea had a specialist reach out to deleted all of the "broken user" credentials from our account.  We then sent a new invitation to the. new time tracker and everything now works fine.  

I'm frankly flabbergasted that no one with regular tech support knew anything about this problem.  I literally spend over 48 hours over consecutive days with regular tech support either in chat sessions or on the phone (mostly waiting on hold for hours) where no one could tell me how to fix this.  I got random answers such as:

(1) QBO had deleted the time tracking function from the product at the beginning of the year and that I would have to add an additional subscription for all of my employees to Timesheets at $$$$$ per month;

(2) I was over the "user limit" (even though the website clearly states that there is not a user limit for time trackers.

(3) I had set up the employee incorrectly.

If anyone needs the contact info for the VERY HELPFUL folks in the Office of the President, just let me know.