At the home page it is announced as "Wikimapia is turned off for some time (days or even weeks). Stay tuned. Explanation later."
The reason might be Ukraine-Russia War or related attacks.
https://www.nextinpact.com/lebrief/68555/wikimapia-ne-repond...
https://www.indiatoday.in/world/russia-ukraine-war/story/osi...