fix: better diagnostics for cookie auth failures

- Detect missing sessionid cookie and log clear error
- Improved instructions for both auth methods

instagram_monitor.py

@@ -58,7 +58,21 @@ class InstagramMonitor:
                 logger.info("Session loaded from cookies.txt")
                 return True
             except Exception as e:
-                logger.warning(f"cookies.txt invalid: {e}")
+                logger.warning(f"cookies.txt invalid or missing sessionid cookie: {e}")
+                # Check what cookies are actually in the file
+                try:
+                    import http.cookiejar
+                    cj = http.cookiejar.MozillaCookieJar(str(cookies_path))
+                    cj.load(ignore_discard=True, ignore_expires=True)
+                    cookie_names = [c.name for c in cj]
+                    logger.info(f"Cookies found in file: {cookie_names}")
+                    if "sessionid" not in cookie_names:
+                        logger.error(
+                            "cookies.txt is missing 'sessionid' cookie. "
+                            "You must be logged into instagram.com in the browser before exporting."
+                        )
+                except Exception:
+                    pass
 
         # Method 3: load cookies.json exported from browser extension
         cookies_json_path = Path(config.download_dir) / "cookies.json"
@@ -80,9 +94,10 @@ class InstagramMonitor:
             except Exception as e:
                 logger.error(f"Direct login failed: {e}")
                 logger.info(
-                    "Use cookies.txt or cookies.json instead. "
-                    "Export from browser: install 'Get cookies.txt LOCALLY' extension, "
-                    "go to instagram.com, export, put file in /data/downloads/cookies.txt"
+                    "Instagram blocks most automated logins. "
+                    "Use one of these methods instead:\n"
+                    "  1. Run 'instaloader --login=USERNAME' on host, copy session to data/\n"
+                    "  2. Export cookies from browser (must have sessionid cookie)"
                 )
                 return False