No offline map visualization at all.

Hi, I bought the Osmand+ at half years ago, and it worket well for months, till now. A couple of days ago I started the Osmand+ application, as I used to, to see the offline map. But only a grey background visualized, so I checked that all my offline maps, and yes, they are present on my SD card, moreover, I could update them via the app, so i'm done with the offline map update, and the application update as well, if I check the offline maps via osmand+ "settings/manage map files" menu, it can see offline (vector) maps 6148MB, so theoretically they are present, and readable by the app. But, if I start the "map" menu, there is always only a grey screen appear instead of map graph. Sometimes (I don't actually revealed the real reason and connection behind of the event, to say "when" do that) a short time message appears, and say: "Offline vector map present for this location. To use activate 'Menu'--- 'Configure map'--- 'Map source'---'Offline vector map...' " But, actually if I change the map source according to the message above, or whatever else, nothing is happen, the grey screen stays, regardless the source selection. I tried to set some other options, like map transparency without any success....:( My device is a routed ZTE Grand X Pro, I have to mention, that the device tuchpad+screen was replaced a couple of days ago, but I don't expect any connection with that, only if it can be an issue that the SD card (with offline map contains) was removed for a while.... Please help me out, what should I do the bring it back alive????