In Safari, Apple has a default setting (Prevent Cross-Site Tracking) that prevents advertisers from putting a cookie on your browser, it is called Intelligent Tracking Prevention.
Adobe looks for a cookie put on the computer by Liscio, which delivers the fillable document (eDoc). With Prevent Cross-Site tracking turned on, Safari blocks the eDoc from appearing. This effects all Adobe products. If an eDoc cannot be accessed in Liscio while using the Safari browser, the Prevent Cross-Site Tracking setting must be turned off.
If you prefer not to turn off the setting, Chrome, Firefox, and the Liscio Mobile App can be used to access eDocs.
Source: https://techcrunch.com/2017/09/15/apple-defends-new-ad-tracking-prevention-measures-in-safari/