mobile app failed to local wifi on iPhone

I have just had my GivEnergy PV/Battery/Inverter system installed and commissioned and although it all seems to be functioning the App on my iPhone refuses to work with the "Home" button selected. The "Local Search Failed, No Home connections were found" message shows I have tried all manner of changes based on other people's suggestions but no luck.
The dongle appears on my router's list of devices (as HF-A21) and I can connect to it from my browser (which is connected to the router's wifi) via the IP address in the device list.
The only way I have managed to get the app to connect is to change the iPhones wifi to be that of the dongle itself. It then will work in "Home" mode.
I don't want to connect my phone to the internet via the dongle so I need to try and resolve this issue.
Has anyone else has this problem? and if so have you managed to resolve it?

SteveMcc first thing with the iPhone app is to make sure you've given it location permissions (I think it was). Then, go to the hamburger menu > Settings > Local Monitoring and try to scan for your inverter. If this doesn't work, switch Search for inverters manually on and add the IP address into the box below. That usually does the trick

Make sure you don't have a VPN activated on your phone - it won't find it locally if it does. Or at least, mine won't.

Cdent I have tried all those things but did it again just to make sure. Still no joy.
One thing I have noticed though, when looking at the devices attached to my router the dongle device (HF-A21) is not always in the list. i refresh the list and it appears and then disappears and sometimes just has the name of "UNKNOWN". I wonder if the wifi between the dongle and my router is flakey. Although the distance between the two devices is only one room so it should be OK.

PS: From my laptop, I can ping the IP address of the dongle successfully so it does seem to be registered with my router.

Update: I checked the app last night and it was working with my phone connected to the dongles wifi but decided to switch my phone back to the routers wifi and surprisingly it worked on the Home setting. Now almost one day later it is still working and allows me to switch between Home and Away (not the Ausie soap!) and it still works. Seems to be one of those issues that you are never sure what was done that fixed the issue, or whether it was timing issue or that something between the dongle and the router has changed. So although the problem has been resolved I could not tell anyone what fixed it.