Some tips:
Try disable/stop Proxy, VPN, Antivirus software, Firewall (if you are using)
Try rebooting the Modem, Router, PC
Execute "ping download2325.mediafire.com" from the command prompt and check whether there is a response from the server
Try these download managers https://filehippo.com/software/file_transfer/download_managers/
> I tried to choose the steam option but it didn't detect MCC.
Due to a change in a Steam update, our ability to search its Library folders for MCC broke. Steam changed the location of the file that stores the list of Library folders. I've since implemented a fix, but our Release workflows are broken.
> I instead tried to install an old disc of Halo I had sitting around, put in the CD key, it installed, all good. I start up the executable, install Halo SPV3 and get the words "Your CD key is invalid" and I can't fix that.
The only reasons it wouldn't work after the Loader successfully found your Retail (CD) or Custom Edition license in the Windows Registry is because the no-DRM patch failed to apply to SPV3's haloce.exe. Either the Installer failed to enable the setting in the Loader's config file or the Loader was denied access to haloce.exe. This issue can happen with any Activation method other than the passive detection of Halo Custom Edition's license key in the Windows Registry in which case the DRM patch in unnecessary. In the case of the Loader being denied access to haloce.exe, this is caused by either insuffucient permissions (unlikely) or the file was locked/in-use by another process. You can forcefully unload/unlock haloce.exe via an app like LockHunter or Process Hacker 3.
Install Net Framework , try comatiblity mode and open your console and insert this command chimera_reset.
try the console command first.
Ok I got it working. I Downloaded the 3.1 update for halo spv3 and also updated my .NET Framework work to 4.6.2 from here https://www.microsoft.com/net/download.
Then I tried to install OpenSauce though the installer again, This time it worked. I updated spv3 to 3.1 and loaded up the level halo. picked up the visor and bingo it now works. Im not sure if the proplem was Where I had to install Opensauce manually the frist time or if the net.frame had something to do with it. Or even the patch. Just thoght I would pass this info along in hopes it might help someone.
Can you try out the third-party download manager? These things were found
Android https://play.google.com/store/apps/details?id=org.zloy.android.downloader&hl=en
iOS https://itunes.apple.com/us/app/downloader/id835382053?mt=8
if you don't buy/own Halo PC & use SPV3 thats piracy! buy it to day
using a key found online is just bypassing there anti-piracy system