I am having same issues on Tab S with 2.8.1, with P4. Last Evening I went by the local park office, connected to wifi, opened dji go map, expanded to max resolution in the area I was going to fly, then closed app, turned off wifi, put tablet in sleep. I drove to a different area of the park with no wifi around, did normal start up, turned on location on Tab S, and started to fly in beginner mode. NO MAP. After flying out battery, and checking various functions, landed, replaced battery, changed out of beginner mode, flew around in P mode, changed battery, enabled multi mode, flew around in P and S, I got side tracked and forgot to check out A.
Any way, some where on the second or third battery, (didn't note exactly when) I noted I had a working map in hybrid view same as I looked up on wifi earlier.
To check this morning, I opened the app and zoomed using wifi several miles away, but set as my intended flying site. Started in Beginner mode again, switched off, flew awhile In P, enabled all flight modesand flew some more. I wanted to see if any of the settings made any difference. No map at all today.
As far as I know there is no action required to "cache" the map other than pan to desired area, and zoom to desired resolution.
I do not have a cache map option in settings, the only cache option I have is to cache video.
Hopefully, some one can post a answer resolving our no map issues.
SHUAN