I recieved a new CrystalSky 8.75 inch ultrabright, this week, charged the batteries, performed all updates and am running the latest firmware and DJI Go4 app. The tablet and app are working properly except that the GO4 app does not display Mapbox maps nor is it possible to download offline maps. Is there a fix for this problem?

here you go

I have the same issue, I've reset, restarted and done everything I can think of, and I've looked at every post - including the one above...., which is not a solution.  I really need to have maps.  I follow the instructions shown below, but where that first world map appears, my simply "thinks" you know, that rolling circle, nothing ever opens or downloads.  I have been able to down load other things, but map box just does not work!  Help would be greatly appreciated.

Welcome to the disappointment that is CrystalSky... here's my prediction, it'll never work 100%, there will always be glitches, i.e.permanent  "MAP LOADING" on your flight records .. rare and VERY LATE updates, same copy paste responses from DJI mob that are a joke and almost insulting your intelligence (thanks for your understanding) and to add salt into the wound... the ultra will burn out sooner than later, you'll be put through hoops before DJI does anything and you'll be without a CrystalSky monitor for 4-6 months at which point you'll receive a different monitor not the one you sent and it'll be all over again until warranty runs out and you throw it away...
At which point I recommend you stay away from the so called "Smart Controller"... should be called Controller for Suckers that never learn...

mAIRs Posted at 10-8 22:34
Welcome to the disappointment that is CrystalSky... here's my prediction, it'll never work 100%, there will always be glitches, i.e.permanent  "MAP LOADING" on your flight records .. rare and VERY LATE updates, same copy paste responses from DJI mob that are a joke and almost insulting your intelligence (thanks for your understanding) and to add salt into the wound... the ultra will burn out sooner than later, you'll be put through hoops before DJI does anything and you'll be without a CrystalSky monitor for 4-6 months at which point you'll receive a different monitor not the one you sent and it'll be all over again until warranty runs out and you throw it away...
At which point I recommend you stay away from the so called "Smart Controller"... should be called Controller for Suckers that never learn...

Could not have stated it any better. Crystalsky could have and still could be an awesome device if they would just show it a little love ! But I’ll probably be dead by the time the next update rolls out. For that I won’t even look at a smart controller. Hahaha, no way !