> For the complete documentation index, see [llms.txt](https://lifesteal-1.gitbook.io/lifesteal/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://lifesteal-1.gitbook.io/lifesteal/lifesteal-en/minecraft/advanced-technical-issues.md).

# Advanced technical issues

***

### 1️⃣ Invalid Session / Public Key Signature Invalid

#### Symptoms

* Immediate disconnection from the server
* Message: `Invalid session` or `Public key signature invalid`

#### Solutions

1. Make sure you are properly logged into your account **Microsoft / Mojang** in the official launcher.
2. Completely restart Minecraft (close all windows).
3. Check that you are using the **correct game version (1.21.4)**.
4. If the problem persists, restart your PC.

***

### 2️⃣ Instant kick upon entering the server

#### Symptoms

* You are kicked just after joining the server
* No specific message or “unknown reason”

#### Solutions

1. Check that your **resource pack is accepted**.
2. Update your **launcher** and **mods** if you are using any.
3. Check that your **username** does not contain prohibited special characters.
4. Restart the server or your game if necessary.

***

### 3️⃣ Lag / low FPS

> For this section, see [`Lag or low FPS: what to do?`](https://lifesteal-1.gitbook.io/lifesteal/minecraft/lag-ou-faible-fps-que-faire)

***

### 4️⃣ Connection errors / Timeout

#### Symptoms

* Unable to connect
* Message: `Connection Timed Out`

#### Solutions

1. Check your **Internet connection** (Ethernet cable recommended).
2. Close downloads or videos running in the background.
3. **Do not use a VPN**, the server has an **anti-VPN** active that blocks connections via VPN.
4. Check that the server is not under maintenance: [Discord LifeSteal](https://discord.gg/3vMguzZFbJ).

***

### 5️⃣ Other common issues

* **Incompatible mods** : disable them one by one to find the culprit
* **Outdated Java** : update to the latest version (Java 17+)
* **Custom launcher** : make sure it is up to date and properly configured

***

🎯 **General tip**\
If you can't find a solution, open a **Discord ticket** in [**`『📩』tickets`**](https://discord.com/channels/1331635184839430215/1331635185435021428) or [**`『📩』priority-tickets`**](https://discord.com/channels/1331635184839430215/1422312038264475731) to get direct assistance from the staff.


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