Thanks. I've been messaging them back and forth for a couple of days and we did figure it out. But I still have some questions as to what happened and why their fix worked.
They provided a link to:
http://my-site-name.com/wp-admin/admin.php to replace the error message page. I went their directly, put in my license and it registered on the whole network fine. We just got it done, so it's solved. I'll close the ticket giving you the opportunity to help me understand what happened.
Carl Hancock at GF (by the way, they are great; excellent support; I've had it for two years; absolutely the best) said that:
"Gravity Forms will not show up on individual sites of a Multi-Site configured WordPress install unless it is network activated OR unless an admin selectively activates it on specific sites.
"You cannot enter your license key and configure the Gravity Forms site settings from the Network Admin because the Network Admin is NOT a site. It's a special admin area that isn't itself a "site" in WordPress.
"The Gravity Forms Settings where you enter your license key are site specific. The data is stored in the wp_options table for that site. The Network Admin is NOT a site and does not have it's own wp_options data.
"For this reason you need to either network activate Gravity Forms or activate Gravity Forms on specific sites and THEN you must enter the Gravity Forms license key on the Gravity Forms Settings page of each individual site..."
But, I've found differently. I have a number of network sites. All installed, activated and registered GF through the Network Administration area. Once registered there, all subsites have GF as a WP Dashboard item called "Forms". There is NO area in the subsites under Plugins that shows the GF in the menu OR any way to install a plugin from the sub site.
What am I missing here? Carl sent over a url for the page to get the license activated, but that page never came up without the .../network/... in the url when I attempted registration on the one Plugins page that showed GF, the one on Network Admin>Plugins. That was where the problem was. Every time I hit the register button, I got the error result with .../network/.. in it.
I still don't get it. I was hoping you might have some idea.
Thanks again for your help