Please visit AccessMedicine through your institution’s website, e.g. your library. This will authenticate you with your institution as a current user (you will probably be prompted to login with your institutional credentials at least once if accessing from off-campus).
Once in AccessMedicine, sign in or create your MyAccess profile (upper-right). Please sign into your MyAccess profile in this manner at least once every 90 days to keep your account active.
After you have done this, please try re-installing the app on your mobile device.
Please email firstname.lastname@example.org if you need further assistance.