diff --git a/game/addons/sourcemod/scripting/sbpp_main.sp b/game/addons/sourcemod/scripting/sbpp_main.sp
index 75746aa6c..d793f32fd 100644
--- a/game/addons/sourcemod/scripting/sbpp_main.sp
+++ b/game/addons/sourcemod/scripting/sbpp_main.sp
@@ -1624,8 +1624,7 @@ public void AddedFromSQLiteCallback(Database db, DBResultSet results, const char
 
 	} else {
 		// the insert failed so we leave the record in the queue and increase our temporary ban
-		FormatEx(buffer, sizeof(buffer), "banid %d %s", ProcessQueueTime, auth);
-		ServerCommand(buffer);
+		SBPP_BanIdentity(auth, ProcessQueueTime);
 	}
 	delete dataPack;
 }
@@ -1692,7 +1691,7 @@ public void VerifyBan(Database db, DBResultSet results, const char[] error, int
 
 	if (results.RowCount > 0)
 	{
-		char buffer[40], Name[MAX_NAME_LENGTH], Query[512];
+		char Name[MAX_NAME_LENGTH], Query[512];
 
 		// Amending to ban record's IP field
 		if (results.FetchRow())
@@ -1731,9 +1730,15 @@ public void VerifyBan(Database db, DBResultSet results, const char[] error, int
 
 		db.Query(ErrorCheckCallback, Query, client, DBPrio_High);
 
-		FormatEx(buffer, sizeof(buffer), "banid 5 %s", clientAuth);
-		ServerCommand(buffer);
-		KickClient(client, "%t", "Banned Check Site", WebsiteAddress);
+		// Ban via BanClient() so SourceMod bans with the engine's own auth
+		// string. The raw "banid <STEAM_...>" console command is rejected by
+		// some engines (e.g. Synergy), which left the player unbanned.
+		// SetGlobalTransTarget() keeps the message in the client's language,
+		// which KickClient() used to do for us.
+		char BanReason[256];
+		SetGlobalTransTarget(client);
+		FormatEx(BanReason, sizeof(BanReason), "%t", "Banned Check Site", WebsiteAddress);
+		BanClient(client, 5, BANFLAG_AUTHID, BanReason, BanReason, "sbpp");
 
 		return;
 	}
@@ -2595,11 +2600,7 @@ stock void UTIL_InsertTempBan(int time, const char[] name, const char[] auth, co
 	delete dataPack;
 
 	// we add a temporary ban and then add the record into the queue to be processed when the database is available
-	char buffer[50];
-
-	Format(buffer, sizeof(buffer), "banid %d %s", ProcessQueueTime, auth);
-
-	ServerCommand(buffer);
+	char kickMessage[512] = "";
 
 	if (IsClientInGame(client))
 	{
@@ -2608,9 +2609,13 @@ stock void UTIL_InsertTempBan(int time, const char[] name, const char[] auth, co
 			FormatEx(length, sizeof(length), "permanent");
 		else
 			FormatEx(length, sizeof(length), "%d %s", time, time == 1 ? "minute" : "minutes");
-		KickClient(client, "%t\n\n%t", "Banned Check Site", WebsiteAddress, "Kick Reason", admin, reason, length);
+		// KickClient() used to localise this for us; keep doing so.
+		SetGlobalTransTarget(client);
+		FormatEx(kickMessage, sizeof(kickMessage), "%t\n\n%t", "Banned Check Site", WebsiteAddress, "Kick Reason", admin, reason, length);
 	}
 
+	SBPP_BanIdentity(auth, ProcessQueueTime, kickMessage, client);
+
 	char banName[MAX_NAME_LENGTH], banReason[256], query[512];
 
 	SQLiteDB.Escape(name, banName, sizeof(banName));
@@ -2838,4 +2843,113 @@ stock void AccountForLateLoading()
 	}
 }
 
+/**
+ * Converts a SteamID2 ("STEAM_X:Y:Z") into a SteamID3 ("[U:1:W]").
+ *
+ * The universe is always rendered as 1 (public), mirroring how SourceMod
+ * itself renders AuthId_Steam3: mods that set "UseInvalidUniverseInSteam2IDs"
+ * render public-universe accounts as STEAM_0, so the X field is not a
+ * trustworthy universe.
+ *
+ * @return true on success, false if the input was not a convertible SteamID2.
+ */
+stock bool SBPP_Steam2ToSteam3(const char[] steam2, char[] buffer, int maxlen)
+{
+	if (strncmp(steam2, "STEAM_", 6) != 0)
+		return false;
+
+	// "STEAM_ID_PENDING" / "STEAM_ID_LAN" carry no account id.
+	if (strncmp(steam2[6], "ID_", 3) == 0)
+		return false;
+
+	char parts[3][12];
+	if (ExplodeString(steam2[6], ":", parts, sizeof(parts), sizeof(parts[])) != 3)
+		return false;
+
+	if (parts[1][0] == '\0' || parts[2][0] == '\0')
+		return false;
+
+	int y = StringToInt(parts[1]);
+	int z = StringToInt(parts[2]);
+
+	// %u, not %d: account ids past 2^31 would otherwise render negative.
+	FormatEx(buffer, maxlen, "[U:1:%u]", (z * 2) + y);
+	return true;
+}
+
+/**
+ * Bans a player by authid regardless of whether they are still connected.
+ *
+ * Uses BanClient() when the player is in game so SourceMod bans with the
+ * engine's own auth string (SourceMod feeds "banid" the string the engine
+ * itself reports for that player). Some engines (e.g. Synergy, appid 17520)
+ * reject the "STEAM_" format passed to the "banid" console command, which
+ * silently dropped the ban. When the player is offline we ban by identity
+ * using the SteamID3 form for the same reason.
+ *
+ * @param auth          SteamID2 of the target.
+ * @param minutes       Ban length in minutes.
+ * @param kickMessage   Message shown to the target if still connected; the
+ *                      generic "check the website" phrase is used when empty.
+ * @param client        Optional client index hint for the target.
+ */
+stock void SBPP_BanIdentity(const char[] auth, int minutes, const char[] kickMessage = "", int client = 0)
+{
+	if (auth[0] == '\0')
+		return;
+
+	// These are always temporary holds until the database catches up, so never
+	// let a misconfigured length through: "banid 0" is a permanent ban and
+	// SourceMod additionally writes it out to banned_user.cfg.
+	if (minutes < 1)
+		minutes = 5;
+
+	int target = 0;
+
+	if (client > 0 && client <= MaxClients && IsClientInGame(client) && !IsFakeClient(client)
+		&& StrEqual(g_sSteamIDs[client], auth, false))
+	{
+		target = client;
+	}
+	else
+	{
+		for (int i = 1; i <= MaxClients; i++)
+		{
+			if (IsClientInGame(i) && !IsFakeClient(i) && StrEqual(g_sSteamIDs[i], auth, false))
+			{
+				target = i;
+				break;
+			}
+		}
+	}
+
+	if (target)
+	{
+		char message[512];
+
+		if (kickMessage[0] != '\0')
+		{
+			strcopy(message, sizeof(message), kickMessage);
+		}
+		else
+		{
+			SetGlobalTransTarget(target);
+			FormatEx(message, sizeof(message), "%t", "Banned Check Site", WebsiteAddress);
+		}
+
+		// BanClient() kicks on the next frame, so callers passing a global
+		// buffer (g_sSteamIDs[] & co.) can keep using it after this returns.
+		BanClient(target, minutes, BANFLAG_AUTHID, message, message, "sbpp");
+		return;
+	}
+
+	// BanIdentity() rather than a hand-built ServerCommand("banid ..."): it
+	// strips command separators out of the identity and notifies OnBanIdentity.
+	char steam3[MAX_AUTHID_LENGTH];
+	if (SBPP_Steam2ToSteam3(auth, steam3, sizeof(steam3)))
+		BanIdentity(steam3, minutes, BANFLAG_AUTHID, kickMessage, "sbpp");
+	else
+		BanIdentity(auth, minutes, BANFLAG_AUTHID, kickMessage, "sbpp");
+}
+
 //Yarr!