Can access admin page (now), but not any site pages...yii not found http execption Have not accessed my local .test sites in a bit.  I tried today.  I am getting a series of errors.   

At first I could not access any page to include the admin page.  I ran Composer update from the command line (within a site's directory) and then updated Craft from the command line (.\ craft update all).  I can now access the admin page and successfully login, but I am still getting errors trying to access the actual site's home page (or any page other than the admin page).

HTTP 404 – Not Found – yii\web\NotFoundHttpException
Template not found: login

All my templates are located here...(according to Finder)  /Users/myname/Documents/Websites/mysite/templates/index.twig

Where should I start?
I am presuming Craft 3 because of composer, but you didn't say. 

To start with look in your craft templates folder. I would suggest that you simply don't have the template that Craft is looking for. 

If you visit the root of your site this is normally templates/index.twig make sure this is present and has no further includes in it (just until you get it working) 

Also try looking in storage/logs/web.log for errors.