cannot install

[oprogramador]

npx sls plugin install -n serverless-local-schedule gives me the following error.

Unhandled rejection ServerlessError: Trying to populate non string value into a string for variable ${opt:stage}. Please make sure the value of the property is a string.

And when I install serverless-local-schedule with yarn and I add it to the plugins section of the serverless.yml file, it just doesn't work (I have cron(* * * * * *) so it should be run every minute but after waiting several minutes I see nothing is run, looking at the local logs).