If League or TFT won’t launch the League of Legends™ game client after champ select, gets stuck on “Reconnect,” or shows “Game in Progress” with no client opening, this is probably not your internet/GPU, nor something a reinstall will fix. I was stumped with this problem for a while and couldn't find a fix. Hopefully, this saves someone else from going through the same frustration.

Symptoms

  • Riot Client opens fine
  • Valorant works normally
  • League & TFT fail to launch after clicking Accept
  • Stuck on Reconnect (button does nothing)
  • Task Manager shows no League game process running
  • Reinstalling League / Riot Client does nothing
  • Started suddenly after a Windows update (for me: after April 2025)

What Riot Support Told Me

After sending in my logs using the RiotRepairTool(RRT), different suggestions were offered:

  • Reinstalling League/Vanguard
  • Trying different compatibility modes for the various League Clients.
  • Adjusting Network/Registry/Conflicting Antivirus configs
  • System Health / Malware Checks
  • Reinstalling Windows/Taking the laptop to a repair shop (lol... T=T )

None of that helped (I didn't bother with the final suggestions, as it was too much hassle).

How I resolved the Issue

I inspected the client logs with the help of ChatGPT and adjusted the relevant system settings.

Logs Location

C:\Riot Games\League of Legends\Logs\

Check these folders:

  • GameLogs
  • LeagueClient Logs

Open the most recent .log files and search for:

  • ERROR
  • FAIL
  • FATAL

The Key Error

These were the ERROR messages in the logs:

ERROR| rcp-be-lol-gameflow| processSpawnW failed:: The operation was blocked as the process prohibits dynamic code generation.

ERROR| rcp-be-lol-gameflow| Failed to launch the game client: processSpawnW failed:: The operation was blocked as the process prohibits dynamic code generation.

This means Windows security is blocking League from starting, not League itself.

Root Cause

Windows Exploit Protection is blocking League’s game client.

Specifically:

  • Arbitrary Code Guard / Block Dynamic Code

This can suddenly activate after:

  • Windows Updates
  • Security patches
  • Defender policy changes

Other games (Valorant, etc) may not be affected as they launch differently.

THE FIX

Step-by-step (you can ask ChatGPT or any other assistant to guide you through if needed):

  1. Press Windows Key
  2. Search Exploit Protection
  3. Open Exploit protection settings
  4. Go to Program settings
  5. Click Add program to customise
  6. Choose the exact file path
  7. Add each of the following one by one:
    1. C:\Riot Games\League of Legends\LeagueClient.exe
    2. C:\Riot Games\League of Legends\LeagueClientUx.exe
    3. C:\Riot Games\League of Legends\LeagueClientUxRender.exe
    4. C:\Riot Games\League of Legends\Game\League of Legends.exe
  8. For each file:
    1. Click Edit
    2. Scroll to Arbitrary Code Guard (ACG) (may be displayed as Block Dynamic Code in your system)
    3. Tick the Override system settings box
    4. Toggle the switch below it to Off (If not already set to this)
    5. Apply
  9. Restart Riot Client
  10. Launch League → queue → game launches normally

Adjust the file paths above to match your system.

You can also optionally disable (if not already done):

  • Control Flow Guard (CFG) Extra protection against memory bugs → Turning it off is usually low risk for games
  • Data Execution Prevention (DEP) Stops code running where it shouldn’t → Basic protection, but rarely needed for League
  • Force Randomisation (ASLR) Randomises memory locations → Turning it off is low–moderate risk
  • Code Integrity Guard (CIG) Blocks unsigned DLLs → Sometimes interferes with game launchers

Try the above and revert changes if they do not help.
For you, ACG may be the only one that actually matters.

Important Notes

  • Do NOT disable exploit protection system-wide
  • Only disable it for LeagueClient.exe
  • This does NOT damage your system
  • Your global protections (DEP, CFG, ASLR) remain ON

Why This Appeared “Out of Nowhere”

Because:

  • Windows updates security silently
  • League’s launcher relies on dynamic code generation
  • Windows Defender suddenly flagged this behavior, preventing the launcher from functioning properly

------------------------------------------------------------------------------------------------

TL;DR

If You’re Seeing These:

  • Endless reconnect loop
  • Game never launches
  • “processSpawnW failed

The Fix:

League isn’t broken.
Windows Defender is blocking it.
Disable Arbitrary Code Guard/ Block Dynamic Code for LeagueClient.exe, etc only.

  • It's easier to disable Windows Defender. lol.
    parent

    IIRC i tried and didnt work (did this a while back), as just disabling Defender antivirus doesn’t change anything - these mitigations are enforced by the Windows kernel, not Defender’s AV engine. To fully disable them, you’d have to dig into the Group Policy file (gpedit.msc) and then adjust Defender settings? which ends up being about the same effort. At least this way, your laptop keeps some of its default protections.

    parent root

    I reinstalled Windows... downloaded the game 3 times and nothing changed. Always the same crap... after 7 minutes of gameplay, the mouse freezes and I end up dying even though I didn't click. 

    I have a computer and a good internet connection.
    parent root

    Try inspecting the logs for Errors.

    parent root

  • so... you didnt give logs to lolsupport.

    short : add lol to defender + disable ransomware.

    parent

    Hahaha, you think I went back and forth with support multiple times and didnt provide any logs?
    All they suggested were the standard fixes unfortunately: Reinstall, etc etc. When you run the hextechtool thing it automatically creates the logs for you to send so all you need to do is attach them.

    I tried adding league to Windows defender's exclusions list and that didnt change anything, but perhaps it'll work for someone else.

    parent root

  • This is the correct way to handle it, unlike just nuking Defender completely. Adding specific exceptions for the executable is way safer. Solid guide.

    parent