Should anyone else have similar problems, this is what I did to get it working.

1. Set WiFi country to match your country (Start -> Preferences -> Raspberry Pi Configuration -> Localisation)
2. Change Stellarmate hotspot to use a band B/G 2.4GHz channel (Start -> Preferences -> Advanced Network Configuration -> stellarmate -> settings (wheel/cog icon))
I left the channel as default.
3. Reboot RPi
4. Set 10.250.250.2 as the AZGTi Server IP in INDI
5. Use the SynScan app to configure SSID as "stellarmate", password and fix IP to 10.250.250.2