Unable to change hard disk size in VM settings (existing and newly created VMs) – Parallels Desktop 27.0.1 (58670) / macOS 27

[DennisL19]

Environment

Field	Value
Parallels Desktop	27.0.1 (58670)
Host OS	macOS 27
Mac hardware	MacBook Pro M1 Pro
Guest OS	tested with Ubuntu 24.04 and 26.04
Affected VMs	existing and newly created VMs

Description

The size of the virtual hard disk cannot be changed via the VM configuration. The issue occurs with existing VMs as well as with newly created VMs, and also when trying to adjust the disk size manually during the installation wizard.

Steps to Reproduce

1. Shut down the VM completely (not just suspend/pause).
2. Open Configuration → Hardware → Hard Disk.
3. Select Advanced for the hard disk.
4. Open Properties to adjust the size.
5. Enter a new value for the disk size and confirm.

Expected Behavior

The Properties dialog opens, a new size value can be entered and applied via Apply/OK, and the virtual hard disk is resized accordingly.

Actual Behavior

• After selecting Advanced, the dialog containing the size settings under Properties sometimes does not open at all (no window, no error message).
• When the dialog does open, the newly entered value cannot be set: the change is not applied and the previous value remains.
• The same behavior occurs when trying to adjust the disk size manually while installing a new VM.

Frequency: reproducible, occurs with every affected VM (dialog failing to open: intermittent).

Checks Already Performed / Workarounds

• The VM was fully shut down.
• The issue is not limited to one specific VM; it also affects freshly created ones.
• Restart of Parallels Desktop and Mac reboot does not help
• Tested with and without snapshots

Impact

It is currently impossible to resize the virtual hard disk of any VM – a blocker for all VMs that require additional storage space.