Wemos D1 mini pro as wifi accesspoint

Hello everyone,
I’m trying to use a Wemos D1 mini Pro (v 1.0.0) board as wifi access point.
My program works fine with the D1 mini board, but when I use the same sketch with the D1 mini pro I can’t connect to the access point. My network manager shows the SSID but the connection fails and the the SSID disappears.

This is the part of my sketch that creates the AP.

#include <ESP8266WiFi.h>

void setupAP(){
  WiFi.mode(WIFI_AP);
  WiFi.softAPConfig(apIP, apIP, IPAddress(255, 255, 255, 0));
  WiFi.softAP(PROJEKTNAME, password);
}

Does anyone know how to fix that?