diff --git a/src/APIHandler.py b/src/APIHandler.py
index 9a749f7..3bcef72 100644
--- a/src/APIHandler.py
+++ b/src/APIHandler.py
@@ -24,8 +24,16 @@ class APIHandler:
             url = f"{self.elaburl}/{entryType}/{elabid}",
             verify=True
         )
-        if response.status_code // 100 in [2,3]:
+        if response.status_code // 100 in [1,2,3]:
             entry_data = response.json()
             return entry_data
+        elif response.status_code // 100 == 4:
+            match response.status_code:
+                case 401|403:
+                    raise ConnectionError(f"Invalid API key or authentication method.")
+                case 404:
+                    raise ConnectionError(f"404: Not Found. This means there's no resource with this elabid (wrong elabid?) on your eLabFTW (wrong endpoint?).")
+                case _:
+                    raise ConnectionError(f"HTTP request failed with status code: {response.status_code} (NOTE: 4xx means user's fault).")
         else:
-            raise ConnectionError(f"HTTP request failed with status code: {response.status_code}.")
\ No newline at end of file
+            raise ConnectionError(f"There's a problem on the server. Status code: {response.status_code}.")
\ No newline at end of file