This is a known issue related to Shopify and Safari browser, but it can be easily fixed by unchecking the option "Prevent cross-site tracking" in your Safari preferences. To change this setting, open your Safari and, at the top menu, go to Safari > Preferences > Privacy tab. If the option "Prevent cross-site tracking" is checked, please uncheck this option and close the window to save your new setting. See the image below:
Reload the backend of your store and test your new setting. If the problem persists, logout from your store, clear the history of your Safari browser, and login again. To clear your browser history, at the top menu, go to History > Clear History, then click the pop-up menu. To learn more, click here.
For more information about Safari preferences, privacy and cross-site tracking, click here.
Note: This known issue does not affect the front-end of your store and it will not impact your customers' experiences. But if you prefer to not change the settings of your Safari, we recommend to use a different browser to manage the backend of your store.