I'm sorry that you're running into this issue. Please try the following if you on the Mac:
1. Quit Google Web Designer if it's running.
2. Launch Terminal and run the following command (or you can use finder to delete the folder if you prefer Finder > Go menu hold the option key and select Library then browser to Application Support/Google Web Designer/webapp/gwdtemplates folder and delete it)
rm -rf ~/Library/Application\ Support/Google/Web\ Designer/webapp/gwdtemplates
3. Relaunch GWD and see if the templates are downloaded and loaded correctly.
If you are on Windows, delete the following folder and launch GWD again: C:\Users\<yourUserName>\AppData\Local\Google\Google Web Designer\webapp\gwdtemplates
Hope it helps.