0e:00:00:01:00:01:23:e2:27:2c:ac:1f:6b:69:dd:9e
That looks like it matches what you originally posted.
What really matters is what is being sent in the DHCP logs. That is what the ISP will see.
Looks like you have an extraneous space in there. The way to set that is using the web interface as described above. Please don't take this as condescending but don't over-think this. It works fine.
It is impossible to say what is wrong. We have no ideas what specific instructions your ISP is insisting you perform. These questions are really better suited at them then give us EXACTLY what they are telling you to do. then, if possible, make pfSense do that. Else it is just guessing.