Hi — that’s very hard to diagnose from here but a couple of things to check:

• Check you are connected to the new WiFI hotspot before trying to connect to pihole. You can’t connect to it from your existing internal network. Your personal IP address on your laptop/desktop should begin 192.168.4.x and you should be able to ping 192.168.4.1. If so, the network is fine and check http://192.168.4.1/admin.
• Alternatively go to the pi desktop, open the web browser and try: http://localhost
• If you are on the correct network (192.168.4.x) but can’t ping the pi address (192.168.4.1), login to your pi and confirm both the interfaces are up by typing ifconfig You should see eth0 and wlan0 both with valid IP addresses. wlan0 should have an inet of 192.168.4.1. Try pinging that IP from the PI. If any of that is missing or won’t ping locally, something has gone wrong and you’ll need to go back through all the steps.
• If you can ping but not get to the pihole webpage, check pihole is running: ps -ax|grep pihole You should see the process /usr/bin/pihole-FTL running. If not, try sudo service pihole-FTL restart
• If pihole is running, see if you can fetch the page from the pi box itself. Either go to the pi desktop and open your browser to visit http://localhost, or from terminal type curl localhost — You should get returned the HTML from the pihole home page. That will confirm pihole is running.
• Finally, check you don’t have any additional firewalls blocking access to that device on your laptop or desktop. If pihole is running and accessible on the desktop/via curl you are likely either on the wrong network (join your new WiFi one), or you have a firewall blocking access.

HTH!

James