With Star Micronoics models older than the 39449871, you will need to download the Star Micronics app in order to establish auto-connect.
1: Make sure your printer is paired with your iPad.
2: Download the Star Setting Utility app from the Apple App Store.
3: Open the Star Setting Utility app and select your paired printer from the list.
4: Click the Auto Connect toggle in order to to turn on auto-connect, then select Done.
6: To finish the configuration process, turn off printer. Wait 5 seconds and then turn printer back on.
7: Go to Settings on your iPad to reestablish the connection between your printer and iPad.
After the printer and the iPad are connected, they will automatically connect when powered on. You will not need to reconnect every time.