diff --git a/services/appflowy-collaborate/src/group/cmd.rs b/services/appflowy-collaborate/src/group/cmd.rs
index 5bfc8480..32d0bdf6 100644
--- a/services/appflowy-collaborate/src/group/cmd.rs
+++ b/services/appflowy-collaborate/src/group/cmd.rs
@@ -8,7 +8,7 @@ use tracing::{instrument, trace, warn};
 
 use access_control::collab::RealtimeAccessControl;
 use collab_rt_entity::user::RealtimeUser;
-use collab_rt_entity::{ClientCollabMessage, ServerCollabMessage, SinkMessage};
+use collab_rt_entity::{AckCode, ClientCollabMessage, ServerCollabMessage, SinkMessage};
 use collab_rt_entity::{CollabAck, RealtimeMessage};
 use database::collab::CollabStorage;
 
@@ -155,7 +155,11 @@ where
         let origin = first_message.origin().clone();
         let msg_id = first_message.msg_id();
         let object_id = first_message.object_id().to_string();
-        let ack = CollabAck::new(origin, object_id, msg_id, 0);
+
+        // when the group with given id is not found and the the first message is not init sync.
+        // Return AckCode::CannotApplyUpdate to the client and then client will send the init sync message.
+        let ack =
+          CollabAck::new(origin, object_id, msg_id, 0).with_code(AckCode::CannotApplyUpdate);
         entry
           .value()
           .send_message(ServerCollabMessage::ClientAck(ack).into())
diff --git a/services/appflowy-collaborate/src/group/group_init.rs b/services/appflowy-collaborate/src/group/group_init.rs
index 2bc58c98..d759e234 100644
--- a/services/appflowy-collaborate/src/group/group_init.rs
+++ b/services/appflowy-collaborate/src/group/group_init.rs
@@ -11,7 +11,7 @@ use collab_entity::CollabType;
 use dashmap::DashMap;
 use futures_util::{SinkExt, StreamExt};
 use tokio::sync::{mpsc, RwLock};
-use tracing::{error, event, trace};
+use tracing::{error, event, info, trace};
 use yrs::updates::decoder::Decode;
 use yrs::updates::encoder::Encode;
 use yrs::Update;
@@ -200,7 +200,26 @@ impl CollabGroup {
       modified_at.elapsed().as_secs() > 60 * 60
     } else {
       let elapsed_secs = modified_at.elapsed().as_secs();
-      elapsed_secs > self.timeout_secs() && self.subscribers.is_empty()
+      if elapsed_secs > self.timeout_secs() {
+        // Mark the group as inactive if it has been inactive for more than 3 hours, regardless of the number of subscribers.
+        // Otherwise, return `true` only if there are no subscribers remaining in the group.
+        // If a client modifies a group that has already been marked as inactive (removed),
+        // the client will automatically send an initialization sync to reinitialize the group.
+        const MAXIMUM_SECS: u64 = 3 * 60 * 60;
+        if elapsed_secs > MAXIMUM_SECS {
+          info!(
+            "Group:{} is inactive for {} seconds, subscribers: {}",
+            self.object_id,
+            modified_at.elapsed().as_secs(),
+            self.subscribers.len()
+          );
+          true
+        } else {
+          self.subscribers.is_empty()
+        }
+      } else {
+        false
+      }
     }
   }