Mail Preferences blank after latest OS X update

I went through all the steps below, that I found in a similar post.

"depending on wether you have iCloud services on; ever used dot mac or the length of a gray and white cats tail the mail preferences may have been stored in several different places including (but not necessarily excluding other places):

term> find ~/Library/ -type f -name 'com.apple.mail*.plist'

~/Library/Application Support/CloudDocs/session/containers/com.apple.mail.plist

~/Library/Library/Preferences/com.apple.mail.plist

~/Library/Library/Containers/com.apple.mail/Data/Library/Preferences/com.apple.m ail.plist

~/Library/Library/Containers/com.apple.mail/Data/Library/SyncedPreferences/com.a pple.mail.plist

Quit mail, move these into appropriately named desktop folders (so you can tell which one goes where);

Launch mail (wait for it to rebuild its db...); (Preferences window should be find now.);

Quit mail; put the com.mail.apple.plist files back to where you get them. Launch mail."

I can still not access my preferences. I get a blank page with "general" in the header. I can now select my signature within the mail, but as I need to change something in that signature, I really need to get into preferences. Any ideas, anyone?