Use this guide when Nomni POS won't let you change an iPad between Master and Slave, or won't connect a Slave to the Master. Find the message you see on screen and follow the fix. You change modes in Settings > Connection, under Server Mode.
"Enter validation PIN" / "The PIN you entered is invalid"
Changing to Master or to Slave always asks for a validation PIN. The PIN is today's day and month as four digits (DDMM). For example, on 24 May the PIN is 2405. Check the iPad's date is correct (iPad Settings > General > Date & Time, Set Automatically on).
"Unable to Become Master"
"POS already has a Master. Disconnect from it to be promoted to Master": this iPad is still connected to a Master. Remove the Master from this iPad's Server List with the ×, then tap Master again. Only one iPad should be the Master.
"POS is currently looking for a Master" or "POS is currently trying to connect to Master": wait a few seconds until the spinner stops, then try again.
"Running multiple Masters on the same network may make the POS system unstable!"
Another iPad on your network is already the Master, and the message shows its device name and IP. Don't continue unless you're replacing that Master. Keep one Master and set every other iPad to Slave.
"Unable to switch to Slave mode"
"There are unsettled orders in the system": settle or close every open order on this iPad first, then try again.
"There are unsynced orders in the system": sync your orders first. See How do I sync Unsynced Orders?
"Please Disconnect Razor in Device Options": go to Settings > Device Options, disconnect Razor, then try again.
"⚠️ Switching to Slave Mode: This action may disconnect all devices"
Devices are still listed in this iPad's Server List. Remove each one with the ×, then tap Slave again. After the change, reconnect the other iPads to the new Master.
"Local Network Access Required"
Nomni POS needs Local Network permission to find the Master. Tap Open Settings (or go to iPad Settings > Nomni POS) and turn Local Network on, then go back and tap Retry.
"Unable to search for Master POS" / "Unable to connect" / "Unable to Auto Connect."
The iPad isn't on a network, or it can't reach the Master. Check the iPad is on the same Wi-Fi as the Master, then type the Master's DEVICE ADDRESS (for example 192.168.9.20) into the box on the Slave and tap Connect. Typing the address is more reliable than Auto Connect. For more checks, see Slave iPad not connecting to the Master: troubleshooting.
"Device limit exceeded"
You have more devices connected than your subscription allows. Remove devices you no longer use from the Server List, or contact Nomni support to change your plan.
Still stuck?
Contact Nomni support with your Store ID, which iPad is affected, the exact message, and a screenshot of Settings > Connection.