Have any of your Mac’s USB-C ports stopped working in 10.15.4?

A few users are reporting that, following upgrading their Mac to Catalina 10.15.4, one or more of its USB-C/Thunderbolt 3 ports stops working.

Although uncommon, if your Mac suffers this the remedy is straightforward: reset its SMC. That should return function to normal. If it doesn’t then you’d be wise to run Diagnostics in case it’s a genuine hardware failure.