Unable to enroll iPad to ASM via Configurator

Using Configurator 2.17 for Mac on a Macbook Pro (Sonoma).

I've previously been able to add iPads without too much difficulty, however this appears to have stopped working for no discernable reason.

Following all the guides under the sun and following the search hits for the error we get means I end up going round in circles.

I've removed our MDM (Mosyle) from the mix to keep things simple, so the procedure is basically:

Connect iPad via USB (ipad is an older vintage iPad Air on 12.5.7). Wipe or restore to factory with Configurator.

Once done, select and Prepare.

Manual Configuration, tick Add to ASM or ABM. Untick Activate and complete enrollment.

MDM Server - set to "Apple School Manager", which as per an Apple guide is just the default server with unchanged URL.

Organization - set to our school which is verified correct. Have tried recreating this.

Setup Assistant - skip all

Network profile - profile selected here which is either the school WiFi (standard WPA2) or have also tried my mobile hotspot to rule out any firewall or filtering issues).

Click Prepare. Every time we get the same result

"The cloud configuration server could not be verified. [MCCloudConfigErrorDomain - 0x80EF (33007)]

I can see on the iPad that the network profile has successfully installed, but that's as far as I can get.

I don't have any other devices I can try without depriving a teacher of theirs, which I'm unable to do.

Any help or advice gratefully received.