your brawl pack contains the ISO or only some files and a gct?
Like you noticed, SSBB has TitleID6 (yeah, that's the 6 digit ID you reported, so you understood what I meant) is : RSBx01
R = Wii
MC = Mario kart
SB = Super Smash Bros Brawl
E/P/J = region (E= USA, P=EUR, J=JPN)
01 = Nintendo
So, your game probably has TitleID RSBE01 if it's the original and official, unpatched game ISO. And the gct is correctly named RSBE01.gct
Maybe the patching team made a new ISO with a new titleID to prevent interfering with your official SSBB savegame, and you have to use their ISO version to work with that gct file?
But what's strange is that you said you are using a pack, so the files are probably already named correctly.
So, there are multiple possibilities why it's not working :
1. The ISO internal TitleID is not matching the GCT filename
2. The ISO internal TitleID is fine, but the TitleID in the game path (folder name) is different. (example : wbfs/Super Smash Bros [RMCP01]/ <-- RMCP is mario kart, you can do that if you want to list one game multiple times in the loader, with different settings, but the gct must be RMCP01.gct)
3. any mix of wrong path, wrong filename, wrong ISO title ID, and the gct will not work.
the problem you have is maybe because USBLoaders use the TitleID found in the path (folder name or filename), instead of looking inside the ISO. path and ISO are maybe not the same ?
To check the TitleID, you have two methods:
1. computer
Launch Wii Backup Manager
mount your HDD partition
look for your SSBB game, and read the "titleID" column. if it's RSBE01, it's the good TitleID of the official unpatched ISO.
if it's not RSBE01, the ISO is already patched, you need to rename folders and filenames, so the USB Loader will use the correct TitleID.
2. USBLoaders
In USBLoaderGX, go to the "list layout" mode. the one which list all games's titles, and has cover on the left.
under the cover, you should see the TitleID detected and used by USBLoaderGX.
if you don't see any titleID below the cover, you can go to Settings > GUI settings > there's an option which lets you display : TitleId, region, Both, none. select both
The gct filename must match the titleID detected by the loader.