GPO not being applied - powershell

Question

I am using the powershell GroupPolicy module to create and link new GPOs. I have a large number of GPOs to create, and thus I wish to automate the process without having to interact with the Group Policy Editor.
I noticed while creating GPOs through the editor that each policy object would be contained in either one or several XML files or .INI files.
Having noted above, I started creating GPOs with the New-GPO command, passing the -Name and -Domain flags. After the GPO has been successfully created, I would (via my script) generate an XML file containing all of the information that the policy would consume. Shown below is an extract of the XML file that I would create to set up a mapped drives policy.
When inspecting the policy in the editor, everything looks fine. The correct drives are showing up and all of the settings appear to be correct. However, the policy is never applied. If I create an identical policy manually via the Group Policy Editor, all of the policies start working, including the ones that I created with powershell.
The error therefore seems to be that the domain controller is never made aware of the changes, but they get applied when a manual change is made.
I have tried running gpupdate /force, which does not seem to update or propagate the changes
New-Item \\$($MappedDrivesGPO.DomainName)\SYSVOL\$($MappedDrivesGPO.DomainName)\Policies\$("{"+$MappedDrivesGPO.Id+"}")\User\Preferences\Drives\Drives.xml -ItemType File -Force
Set-Content \\$($MappedDrivesGPO.DomainName)\SYSVOL\$($MappedDrivesGPO.DomainName)\Policies\$("{"+$MappedDrivesGPO.Id+"}")\User\Preferences\Drives\Drives.xml $xml
<?xml version="1.0" encoding="utf-8"?>
<Drives clsid="{8FDDCC1A-0C3C-43cd-A6B4-71A6DF20DA8C}">
<Drive clsid="{935D1B74-9CB8-4e3c-9914-7DD559B7A417}" name="P:" status="P:" image="2" changed="2019-04-26 10:41:54" uid="{$guid1}" bypassErrors="1">
<Properties action="U" thisDrive="NOCHANGE" allDrives="NOCHANGE" userName="" path="\\fs1\Projects" label="Projects" persistent="0" useLetter="1" letter="P"/>
<Filters>
<FilterGroup bool="AND" not="0" name="$($domainName)\Drive P Access" sid="$($filterGroupSidDriveP)" userContext="1" primaryGroup="0" localGroup="0"/>
</Filters>
</Drive>
<Drive clsid="{935D1B74-9CB8-4e3c-9914-7DD559B7A417}" name="S:" status="S:" image="2" changed="2019-04-26 10:39:21" uid="{$guid2}" bypassErrors="1">
<Properties action="U" thisDrive="NOCHANGE" allDrives="NOCHANGE" userName="" path="\\as1\Software" label="Software" persistent="0" useLetter="1" letter="S"/>
<Filters>
<FilterGroup bool="AND" not="0" name="$($domainName)\Drive S Access" sid="$($filterGroupSidDriveS)" userContext="1" primaryGroup="0" localGroup="0"/>
</Filters>
</Drive>
</Drives>
I expected the policy to start working as intended after the XML file had been created
The actual result is that the policy appears to be well formed, but never applied

Answer 1

I managed to resolve this on my own, posting here in case someone else runs into the same issue. If you're creating GPOs programmatically and not via the editor, you will have to extend your script/program to add CSE (in this case for drive mapping) and SnapIn GUID to gPCUserExtensionNames.
[{00000000-0000-0000-0000-000000000000}{2EA1A81B-48E5-45E9-8BB7-A6E3AC170006}][{5794DAFD-BE60-433F-88A2-1A31939AC01F}{2EA1A81B-48E5-45E9-8BB7-A6E3AC170006}]
The 0000.. is the Core GPO Engine, 23EA.. is the Preference Tool CSE GUID Drives, 5794.. is Preference CSE GUID Drives.
If you create the policy manually with the desired changes, you can then open dsa.msc, enable advanced features and then view the policy object properties. Under gPCUserExtensionNames you will be able to see the arrays containing the GUIDs that you need to incorporate in your software.