Hello, I had exactly the same error.
After a bit of research into the cause, I was able to determine that the DWD file has a different name for the values.
In the main.js file, a name TTTmax and TTTmin are searched for, but not found.
I replaced the name TTTmax with TX and TTTmin with TN.
The main.js file is in the directory weewx/skins/weewx-wdc/dist/
I changed the file with an editor, search and replace, the name appears once each, restart weewx after the change so that the file is copied to the website.
Harald