Apple today released macOS Catalina 10.15.4 supplemental update which improves the stability and security of your Mac and includes:
• Fixes an issue where Mac computers running macOS Catalina 10.15.4 could not participate in FaceTime calls with devices running iOS 9.3.6 and earlier or OS X El Capitan 10.11.6 and earlier
• Resolves an issue where you may repeatedly receive a password prompt for an Office 365 account
• Fixes an issue where MacBook Air (Retina, 13-inch, 2020) may hang in Setup Assistant or when disconnecting and reconnecting a 4K or 5K external display
• Resolves an issue where a USB-C port in your Mac may become unresponsive
The macOS Catalina 10.15.4 Supplemental Update can be downloaded via the Update feature in Apple’s Mac App Store.