Grammarly (make sure you use www.grammarly.com/edu for the Library-provided premium version!) isn't configured to work on iPads or other mobile devices. However, there is a work-around that allows it to work perfectly on a mobile device.
When you log in to Grammarly from your iPad you get a sad-face “Grammarly is not yet mobile friendly” message.
However, if you tap the "Share" icon (the up-arrow in Safari, or the dot-dot-dot in Chrome), you can click “Request Desktop Site” and it immediately works. See screenshots below as examples.