Just went to clean brew unit and realized that I didn't have the cleansing tablets. I was two steps into the process and now the machine will not let me cancel the cleaning. I cannot make coffee

SOURCE: Brew unit in Miele coffee system CVA615 block

It sounds like the connector or wiring that links the LCD display board on the door to the main PCB inside the coffe maker has become loose or damaged.
This would cause the text displayed to become scrambled.
Its a 26 way connector that is labelled JP16 (on the next model up) and is next to a large IC.

SOURCE: miele CVA 4070 coffee system

I called Miele hot line & here is the solution to fixed the problem... 800-999-1360.

http://www.miele.com/

Whenyou start the cleaning cycle, Don't stop the process by pulling the plug! Turnthe unit off from inside wait 5+ seconds & turn back on and thecleaning cycle should restart... If you do not use a cleaning TAB..Open& shut the LOOSE coffee Door under the drawer (Top Left) and thecycle will continue.

SOURCE: miele coffee maker cva 4070

OK. Here's the deal. I struggled with this CVA 4070 (F 73) problem also recently, and even posted a questions in the cyber world about it. I jiggled, re-cleaned the machine, re-read the Miele manual, and scoured the internet for schematic drawings of this brewing unit's insides. No luck. Finally after finding out I'd have to pay $199 just for a service clown to walk in my front door, I said NYET!!!  I must solve by myself. If I can take apart & fix my Dyson, etc, etc, I WILL DO THIS TOO!!  (MUST HAVE COFFEE>>>)
Pull out the brewer, turn it a quarter-turn to your right, and look at the spot where that small black plastic piece -- shaped like a block "M" or block "W" -- should be situated. Pull it out, if it isn't out already. Don't worry about yanking it out or harming these parts, said the Miele troubleshooter guy in New Jersey on the phone. They're "made from the same plastic used in football helmets."  Okey-dokey. 
This approx. 1.5" wide, blocky plastic piece is part of the "slide" that takes the brewed coffee grounds into the waste container. When positioned correctly, it looks like a block "W,"  with the "wings" ointing up, and slides in just under a brown 1.5" flat piece. A small, down-facing tab on the brown piece clicks into the "W" piece and holds it in place. The "W" should feel fairly solid, although it is not rigidly in place, as the entire mechanism is a movable system to deposit the grounds in the waste receptacle. 
Put everything back inside your CVA 4070 "love" machine, hit "on," and wait for it to go through its warm-up.  No F73 message?  Yeah!  Mission Accomplished. You, like I, have fixed your Miele, saved your family relationships, and saved yourself a bundle from unnecessary service calls.

SOURCE: how do i clean my miele coffee system cva 4070?

I have a cva4075 so this may not be exactly the same, but on the 4075 you open the front of the machine and pull out the left hand plastic container on the top. Underneath on the right hand side you will see a small flap. On the bottom side of the flap is a red triangle sign. That flap is the top of the funnel for the ground coffee. You drop the cleaning tablet into this funnel.

SOURCE: I have a three month old Miele CVA 4066. I have

your brew unit is clogged. It will need to be removed and cleaned every 24 hours as per the owners manual. There is a yellow laminated card in the box with the accessories that shows step by step how to perform the 24 hour maintenance. To prolong the life of the brew unit, make sure the coffee grind size lever is in the middle or to the right of center, rather than the left (fine) side. Also, you only want to use dry beans, preferably espresso beans. Oily beans like french roast will clog that brew unit up very quickly.