Users worldwide cannot connect to Pulse Secure VPN devices after a code signing certificate used to digitally sign and verify software components has expired. The issue affects users worldwide and is caused by an expired code-signing certificate and a bug in the Pulse Secure software that is not properly verifying that executables are signed. Pule Secure says they are working on a fix based on version 9.1R11.x of the client software and hope to have it released by the end of the day. For now, it is recommended that users utilize the Pulse Desktop Client instead of connecting via the browser.
Source: https://www.bleepingcomputer.com/news/security/pulse-secure-vpn-users-cant-login-due-to-expired-certificate/