Usually that error pops up because Telegram wants you to respect its anti-spam and privacy rules. If you’re on a basic group (not a “supergroup”), you’ll hit the 200-member cap, and only mutual contacts can be added automatically. First, convert your chat into a supergroup so you can bump the member limit way higher. Then double-check that the people you’re inviting haven’t blocked you or changed their privacy settings to stop strangers from adding them. If you’re using a bot or script, make sure it’s running under a real admin account (bots themselves can’t add users to channels/groups). Lastly, spread your invites out over time—Telegram throttles mass adds, so pause for a few minutes every 20–30 invites to avoid FloodWait errors. That should clear it up.