Go to the Safari drop-down menu (top left, beside the apple icon).

Select Preferences.

Click Privacy in the top panel.

Uncheck Prevent Cross-site Tracking. (Note: Safari has an interesting glitch. If this is already unchecked, try checking it, then unchecking again).

Refresh your page (if a normal refresh doesn't work, try clearing cache* and refreshing).

If the issue continues after refresh, try going back to the Privacy tab and unchecking Block all Cookies.

Open Settings 

Scroll down and tap Safari

Under Privacy & Security, untoggle Prevent Cross-site Tracking. (Note: Safari has an interesting glitch. If this is already unchecked, try checking it, then unchecking again).

Refresh your page (if a normal refresh doesn't work, try clearing cache* and refreshing).

If the issue continues after refresh, try going back to the Privacy tab and unchecking Block all Cookies

Open Settings

Scroll to the bottom and click on Advanced

Under Privacy and security, click on Site Settings

Click on Cookies and site data

Make sure Block third-party cookies and site data is not toggled

Refresh your page (if a normal refresh doesn't work, try clearing cache* and refreshing).

If that doesn't work, check for an "crossed-out eye" icon in the top address bar and click that to allow third party cookies for the specific website:
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On your Android phone or tablet, open the Chrome app

To the right of the address bar, tap More   Settings.

Tap Site settings  Cookies.

Uncheck Block third-party cookies

Go to the Firefox drop-down menu.

Select Preferences.

Click Privacy.

Under Cookies, select the option 'Accept cookies from sites.'

Refresh your page (if a normal refresh doesn't work, try clearing cache* and refreshing).

Tap the menu icon. This is the icon with 3 bars. On older Android devices you'll have to press the hardware menu key and then tap More.

Tap Settings.

Tap Data Management

Ensure that the switch for Cookies is set to ON (the switch should be blue)