Unable to forward ports to Raspberry Pi, but forwarded ports to Windows laptop work fine over the Internet

In my setup I have a Raspberry Pi, a Windows Laptop and a FritzBox 7490. I'd like to allow RDP to be forwarded to my laptop (which works over the Inteet, tested with remote computer and a port-checker) and SSH / HTTP(S) to be forwarded to my Raspberry Pi (only works inteally using the local network IP address, does not work with a remote computer and port-checker says ports are closed).

Now I don't know what is going on here:

• Does the FritzBox not properly forward anymore? (Forwarding worked a few weeks ago but then stopped working one day)

• Has my Raspberry Pi a wrong configuration after some update?

or

• Has my ISP started to block the ports?

The Raspberry is coected via Wi-Fi to the FritzBox (and the Inteet) and via LAN to my laptop directly (I use my Raspberry to remote wake up my laptop).

How can I find out what the problem maker is and how to fix it?