The graphs are displayed in the web UI after start the Pi where Pi-hole is installed.
I switch off the Pi running Pi-hole with normal shutdown if I’m not at home for some time. The graphs are not displayed in any web UI (Chrome, FF on Windows or Safari on an iPad) after start the Pi. This does not recover if I let the Pi run for some days. Restarting a browser or client does not help to display the graphs. That I expect it’s more a Pi-hole related issue.
The only way to get the Graphs be shown is to restart the Pi with “shutdown -r”. The graphs are displayed on all devices afterwards.
The following debug token is provided after a restart with graphs working.
A Debug Token after a new start after some days while the graphs are not working: