Your issue might be due to using multiple Google accounts under the same Chrome browser. Google can't handle when multiple accounts are logged in, and Chrome extensions, such as Labelmaker, don't work well.
SOLUTION : I recommend creating a new profile in Google Chrome with the account you are using Labelmaker with. This will make sure it'll always work with the right account. It takes only 1 minute to set up. To create a new profile, here's a guide:
https://mailmeteor.com/blog/how-to-create-google-chrome-profileLet me know if it works,