If the hotspot splash page doesn’t load after you configure your Mikrotik router / access point, here’s an easy way to fix:
Start Winbox, connect to your Mikrotik device and go to IP -> Hotspot, then make sure you are on the Servers tab. Select the only entry here and click on the Reset HTML button. Then replace the login.html and alogin.html files in the hotspot directory on the Mikrotik device with these: alogin.html and login.html (don’t open these link, save them instead).
Note for White Label operators: These files use the default customer.hotspotsystem.com URL – you need to replace them with your White Label FQDN before you copy them to your Mikrotik device.