Cannot enter a world with an old save.

Saw this game surfaced on Steam, decided to give it a go. Had an old World back from when i was playing this game in browsers. Game sees my old save (Screenshot 1), but upon entering it makes me choose a side, as if I just started anew. When trying to choose a side and pick a zone for a base (or random placement), a pop-up window appears (Screenshot 2), and nothing can be done about it futher. Is there a chance I can continue my old save?

Above mentioned is actual both for Steam version and browser version, as I tried to run a game in a browser, with a same issue.