I have installed the Healdess version since on my boat I will only be using an iPad to connect to OpenPlotter. How can I download charts since the wi-fi connection is in use with the iPad?
I overcame that problem by using a wifi hub and having two VNC connections then it is possible to switch between both by changeing the server adress to the raspi Ip adress, its a bit messy but you dont have to do it very often. Makesure that HDMI is still accessible just incase things go pearshaped (and have a monitor handy). You could also use your phones hotspot.
What is creating the wifi network which is connected to the internet? If it's is a can you could try connecting with usb. I do that on an android phone.
Have you tried using a different wifi connection or switching to a 3G connection?
One option is to download the charts onto your iPad before you set sail when you have access to Wi-Fi, or to use a mobile hotspot.