I found someone else having this problem here:
cant play custom maps RA3 & C&C 3 + KWAnd I found a potential solution here:
Custom maps not showing up in CNC3 Kane's WrathThe above post talks about Kane's Wrath, but the same idea should apply to RA3.
Summary:This may be caused by a missing registry entry for Red Alert 3 when installed via C&C The Ultimate Collection.
To fix:Note: these fixes assume you are using a 64-bit version of Windows 7.
Option 1: Import Registry Fix- Download the CNCUltimateCollectionCustomMapRegistryFix.zip file attached to this post (see below).
- Open the compressed folder, and execute the CNCUltimateCollectionCustomMapRegistryFix.reg file contained within. This will import the missing entries into your Windows Registry.
- Note: this method should have the same effect as the manual method below.
Option 2: Manually Fix RegistryUse the Windows Registry Editor to add the missing key.
- Type "regedit" into the search box in the start menu, and hit enter.
- Navigate to the following key: HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Electronic Arts\Electronic Arts\
- Then, below, navigate to each key for each game ("Command and Conquer 3", "Red Alert 3", "Red Alert Uprising").
- Under each of the games, an entry named "UseLocalUserMaps" of type "REG_DWORD" with value "0" should be present.
- If UseLocalUserMaps is not present, create it by selecting the following menu option: Edit > New > DWORD (32-bit) value. Name the new entry "UseLocalUserMaps" and hit enter or click something else to save it.
- Repeat the above step for each of the games under the "Electronic Arts" key.
Hope that helps - let us know if it works!
Source of CNCUltimateCollectionCustomerMapRegistryFix.reg:
[code]Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Electronic Arts\Electronic Arts]
[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Electronic Arts\Electronic Arts\Command and Conquer 3]
"UseLocalUserMaps"=dword:00000000
[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Electronic Arts\Electronic Arts\Red Alert 3]
"UseLocalUserMaps"=dword:00000000
[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Electronic Arts\Electronic Arts\Red Alert 3 Uprising]
"UseLocalUserMaps"=dword:00000000
[/code]
Edited by user Sunday, November 25, 2012 11:51:55 PM(UTC)
| Reason: Not specified