Sharing issue - no IP is visible

Hello,

The sharing of folders is no longer working since I have moved.

Before the move the config was the following:

Broadband -- ethernet -- Apple Airport Express - extend network -- wireless -- MacBook

An external USB hard drive is connected to the mac, that was shared in the Sharing menu, with file sharing on there is an IP being shown, and when I added this IP as a network drive on my work Windows PC, it was working fine.

Now we have moved, there is a different ISP, but the setup remained the same, Airport Express connected to the modem via ethernet, connected to the Airport wirelessly with the MacBook, but when I open the Sharing menu, no IP is visible, only the name of my computer, and when I want to access that, I cannot connect. Is there a way to have the IP shown again, so I can reach my data over network?