Currently, we are having problems with the ASM portal. Blank page when Monitors option is selected:
Release : SAAS
Component : APP SYNTHETIC MONITOR ENVIRONMENTAL
The problem was that customer created an invalid (immediate) maintenance window which starts and ends at the very same time.
The issue is fixed after removing the problematic maintenance window.
The current immediate maintenance window functionality has a bug, please do not use it till the hotfix when this problem is fix. It will be few weeks before hotfix is released.