This is due to Apple disabling cross-site tracking by default, please see below steps to resolve this:
Safari for Mac:
- Open Safari if it is not already open.
- Click the "Safari" menu and choose "Preferences" and then "Privacy"
- Depending on your version of OS:
- Click prevent Cross Site Tracking to disable this setting.
Safari for Mobile or Tablet:
- Go to Settings
- Click on Safari
- Privacy & Security
- Turn the toggle 'Prevent Cross Site Tracking' to 'Off'.