I just got this message while trying to print a custom DC: We are sorry but Delivery Confirmation is currently not available for the TO address, please check it for correctness.

Then I got a PM from someone I'm in a game with who also got the same message trying to send a package to me. We both double checked and the address's are correct. Do you know if something is wrong with DC today?

To answer my own question here is the response from one of our fabulous (and swift) live helpers!  Thank you June!

About the Custom DC: This sometimes happens and it is either an error from Endacia, our online postage provider and it often goes away if you try to print again.
Keep trying....one time it took me about 5 tries to print the wrapper.
However, you should check the following site anyway to make sure it is recognized: (it's a zip code lookup to see if you are correct).
http://zip4.usps.com/zip4/welcome.jsp

This is what the Help Center says:
I am getting the message "electronic postage cannot be used for this address". What does this mean?
This message "electronic postage is currently not available for this address" is an error message from endicia.com, our online postage provider, and often it just goes away if the sender tries again to print after a few minutes.
If the address is not validated by USPS, you will also see the above message. In the case of an invalid address, the requestor can go to this site to try to find the "validated" form of his or her address. Printed postage can't be used to send a package to an address that has not been validated by USPS.

I get that sometimes using the pre-printed postage.  It usually goes away after a while. Although it always seems to happen when I have a bunch of labels to print and have already printed  a couple w/postage.