This incident has been resolved.

Following a recent security update, Go>Sign Mobile Application users are required to register their device again. Some users may experience delays in receiving the SMS OTP due to automated security controls temporarily blocking certain phone numbers. These temporary blocks typically clear within 15–30 minutes. If you do not receive the OTP, please wait one hour and try registering again once. We are tracking this issue under Case# 05155641 We apologize for any inconvenience this may cause you. DigiCert Support