This form is read-only unless the system is in the maintenance mode. Maintenance mode can be enabled in this environment by running maintenance job from LCS, or using Deployment.Setup tool locally

You may encounter the warning "This form is read-only unless the system is in the maintenance mode. Maintenance mode can be enabled in this environment by running maintenance job from LCS, or using Deployment.Setup tool locally" on any standard form which will also disable editing the form. The warning clearly says the maintenance mode is disabled. You have to run the following command on VM to enable maintenance mode.

C:\AosService\PackagesLocalDirectory\Bin\Microsoft.Dynamics.AX.Deployment.Setup.exe --metadatadir C:\AosService\PackagesLocalDirectory --bindir C:\AosService\PackagesLocalDirectory\Bin --sqlserver . --sqldatabase axdb --sqluser axdbadmin --sqlpwd AOSWebSite@123 --setupmode maintenancemode --isinmaintenancemode true

In the previous command the AOS is installed in 'C' drive, the database administrator user is 'axdbadmin' and its password is the default password of axdbadmin 'AOSWebSite@123'. You have to run CMD as administrator.