I just went through this exact process to get HTTPS working for my fog deployment. One of the more helpful things, especially for where you are at right now, was to enable debugging on the ipxe build as the file not found error was due to a couple of other issues related to the certificate. Additionally, although it shouldn’t have been necessary, building the CA certificate into the ipxe build solved another issue I had with it. To do the above, using Tom’s script, you would pass CERT and DEBUG to it like so (I used my own CA cert and not the FOG one, so the paths were different for me, but should be correct for you. Additionally, tls is likely the only debug option that you might need, but just in case I included the others):
/root/buildIPXE CERT=/var/www/fog/management/other/ca.cert.pem TRUST=/var/www/fog/management/other/ca.cert.pem DEBUG=tls,x509,certstore
Once built, you’ll of course need to reinstall FOG with the new build. When the client boots, it should give you much more insight into what is happening and why it is reporting the file cannot be found (assuming building in the cert doesn’t solve the issue you’re having). Once it booted, I ran into an issue with the check-in script not understanding the HTTPS redirect, but this is resolved in the working version now (I’m personally on the current release version, with some custom changes that are already in the working version).
Hope it helps.
EDIT: Oh, should probably also point out that if you do try this and eventually get it working, removing the debugging after would be a good idea so your systems don’t spew out debug text on boot.