An issue preventing some external drives from mounting onto a Mac running macOS Sonoma has plagued users for months, and it probably was caused by changes Apple made to drive handling.
Hardware support is a common source of problems for operating system updates, and macOS is no exception. Updates to operating systems can cause some types of devices connected to a Mac or MacBook to suddenly stop working, infuriating users in the process.
In some cases, this is a relatively short-lived issue that Apple corrects quickly.
Read more at AppleInsider.com