Try a different web browser, as well as incognito or private windows.
Try another device, such as another computer or mobile phone.
Try another internet connection (switching to a cellular network on a phone rather than wifi, for example)
Ensure you do not have any firewalls or pop up blockers enabled on the device as these can interfere.
It is also good practice to check if we are experiencing any known live issues on our Shopify Status page.
Once you have run through these steps, let me know how this goes!
Hilary | Community Manager @ Shopify - Was my reply helpful? Click Like to let me know! - Was your question answered? Mark it as an Accepted Solution - To learn more visit the Shopify Help Center or the Shopify Blog