In workspace, to maintain the timezone as UTC across all workspaces. I created the GPO settings, suggested by the aws. but the gpo rule is applying on few workspaces but it is not working on others

Hello The first step would be to ensure that all workspaces are receiving the GPOs as intended. You can run gpupdate /force from the command line to force the WorkSpace to update the Group Policies then from an Amazon WorkSpace that is showing the correct settings run gpresult /h in an elevated command prompt and output that to a file locally. Do the same for a WorkSpace that is not showing the correct result. Compare the 2 outputs and see if they are both receiving the same policies. If there are differences, make sure both computer objects are in the correct Organizational Unit (OU) in Active Directory.