Most loader stops come down to Windows and BIOS settings. "Please make sure PIN is not set in Windows sign-in options and manually disable Hyper-V" takes four moves. Take the PIN and password off your system login, switch virtualization off in the BIOS, run the vendor's PowerShell commands and then switch it back on. "Please disable secure boot in the BIOS" wants Secure Boot turned off. With "Please enable Intel VT-X / AMD-V in the BIOS", virtualization is off, and AMD motherboards often list that setting as SVM mode.
Hardware errors stand apart. "Failed to map memory" means the PC has under 12 GB of RAM or startup programs have eaten it: trim the autostart list and reboot, and in stubborn cases AutoRuns helps. If the sticks physically add up to less than 12 GB, the vendor offers a refund, and the same goes for "AES instruction set is not supported": without the AES set in the processor, the build will not run.
When you see "Make sure all antiviruses are disabled", remove any outside antivirus and switch off real-time protection together with SmartScreen. Windows 11 users also get two reg files in the guide, Turn_ON and Turn_OFF; run them one at a time with a restart between them. If the loader vanishes without showing any error, the library pack from the guide was never installed.
Sometimes the loader does its job, but the menu ignores clicks or only opens on the second or third try. Check that Steam is running without administrator rights and that NVIDIA or AMD is the only overlay left on the system. Radeon owners occasionally get an AMD library error: update the libraries, and if that changes nothing, swap the DLL inside the AMD Software folder following the guide.
After a Siege patch the menu can vanish entirely: most likely the build has gone in for an update, which the status on this page will reflect. While you wait, verify the game files. If Siege crashes to a blue screen or your account gets banned mid-match, message the procheat chat with a screenshot of the error text.