Fred, I can't help you with why it won't go to full screen, but can say it's my favorite of all my electronic charts for navigation. I up loaded it on my old IPad 2, when it first came out for around $50, but if I remember correctly, I also payed for the extras such as auto routing & others. When I bought the IPad Pro, I put Navionics on it off there share device program too at no cost. Last spring my iPad 2 had a glitch & I had to reload everything including Navionics. It loaded just fine along with all the maps & works just like the pro, only slower. I love the simple way to auto route a destination, the tracks recording & the tides & currents information is also intuitive with locations wanted to see quick & easy. The present problem for me & one I can live with, is it can't be updated without switching to the now annual fee system. It does quite often ask me do update, which I ignore. I prefer it to the Garmin app & my other plotters are Garmin. I like it enough, that if or when it will no longer work as it does now for me, I will go to the yearly annual fee to retain its it's use.
On the road for navigation, I've been using Garmin's Navigon App on the IPad. I really like it, but now, I recieved notification from Garmin, that it is being discontinued & will only work for 2 more years with no ability to update during them.
Jay