HI solo60,
I know is late to solve your problem but can be of help for others that still use Windows Live Mail 2012 also on the latest Windows 10.
Normally I don't have problems to print mail from WLM but sometimes one mail won't.
This is my workaround.
- reply to the mail you can't print but don't send it, instead Save it using menu File, Save, so it will be filed into Drafts
- close the mail
- go to the Drafts folder, select the just created draft, don't open it
- right click on it with the mouse e select Print or menu File, Print
HTH