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I check Web Application Firewall and I'm not getting a Security Exception.

This means that anything you set in the Admin Tools component and plugin (possibly barring the .htaccess Maker) cannot be involved.

I expect that .htaccess file could be restricting the Redirect?

How can I verify?

No, it cannot. It would block the entire request with 403 Forbidden. Instead, you either get a constant redirection back to the same URL (which means something between Easy Social and your site's menu structure is not quite right) or an Access Denied which is a Joomla! error. Since both the redirects and the Access Denied come from Joomla! this is not a .htaccess issue.

At this point you have disproved any connection between this issue and Admin Tools. It looks like something you'd need to ask Stack Ideas about.

Side note: If you are trying to use the same URL many times I expect that at some point you'll start receiving get Access Denied. Why? Because I suspect the key is either single use or has an expiration limit. Otherwise an old link could be used years later to backdoor into someone's account. This is fundamental security and I expect that Stack Ideas, being a demonstrably responsible software company, has taken into account. Therefore I think your issue is that the URL does work but leads into a redirect loop which is either a bug in the component or something in the way you've set up menu items. I've had that kind of fun with our own frontend software (Akeeba Release System mostly) used on our site: an unfortunate menu hierarchy would cause a redirect loop. Fixing the SEF router that caused the loop broke downloads so we had to change our menu structure and make liberal use of aliases.