Can't drag windows to second external monitor

[uabramov]

Thank you for the suggestion.

Unfortunately, this does not appear to be an arrangement issue within macOS. The displays are not being detected at all after updating to macOS 26.5.

Prior to the update, the FQQ quad monitor setup was functioning properly. Since updating, the unit no longer initializes or appears in Display Settings, even after reinstalling DisplayLink Manager, reconnecting cables, rebooting, and re-granting permissions.

This appears to be more of a DisplayLink/macOS compatibility issue rather than a display arrangement configuration problem.

If anyone has found a confirmed workaround specifically for FQQ or DisplayLink devices on macOS 26.5 with Apple Silicon (M3 Max), I would greatly appreciate the help.