Unfortunately Apple likes their cryptic errors so it is hard to say the exact issue, but it does mean you have some sort of networking issue with your Mac or your network/Internet connection.

Regarding your networking issue try a PRAM Reset (hold the PRAM Reset for at least three chimes so it activates several times). The other volumes shown on your Fusion Drive are completely normal starting with macOS 10.15 Catalina (macOS 11.1 Big Sur adds some other volumes as well): I personally would break the Fusion Drive and set up the Fusion Drive again from scratch and restoring from a backup or clone: Supported OS: Windows 11, Windows 10, Windows 8.From your First Aid report: warning: MT mapping (0x4000006fc7276 -> 0x11c1ae3, 1, C) is not completely referenced warning: MT mapping (0x4000006fc7277 -> 0x11d2cd8, 2, C) is not completely referenced Too many warnings of this type generated suppressing subsequent ones.Technical Details and System Requirements To launch the popup menu, click the QAP icon in the Notification zone, hit the Middle Mouse Button, or press Windows+W (you can change these triggers in Options). Assign favorites or submenus to keyboard or mouse shortcuts or group favorites and launch them in one click.

You can gather related favorites in the submenus. Launch your most used applications, documents, or websites instantly with this easy popup menu and mouse/keyboard shortcuts manager. This program lets you move like a breeze between your frequently used folders and documents, saving thousands of clicks while browsing your favorite folders in Windows Explorer or file dialog boxes. Free Download Quick Access Popup standalone offline installer for Windows is a multi-purpose launcher and folder switcher.

Quick Access Popup 11.6.2.3 download the last version for windows