Hi,
There are two group policy which could limit the roaming profile size:
Limit profile size
User Configuration\Administrative Templates\System\User Profiles
Limit the size of the entire roaming user profile cache
Computer Configuration\Policies\Administrative Templates\Windows Components\Remote Desktop Services\Remote Desktop Session Host\Profiles
Kindly check if these policies have been updated successfully. Or you could run gpupdate /force after enable above policies.
Reference link:
Additional Policy Settings That Are Related to User Profiles
https://learn.microsoft.com/en-us/previous-versions/windows/it-pro/windows-server-2003/cc781862(v=ws.10)?redirectedfrom=MSDN#additional-policy-settings-that-are-related-to-user-profiles
Moreover, there is a KB talking about the GPO "Limit the size of the entire roaming user profile cache" Group Policy setting does not work in Windows Server 2008 R2
https://support.microsoft.com/en-us/help/2575946/limit-the-size-of-the-entire-roaming-user-profile-cache-group-policy-s
Thanks,
Jenny