Files save error in Jupiter after upgrade

After upgrading to 1.9.0 I can not save notebooks instead I get a dialog saying "'_xsrf argument missing from post"

Please see image below.

Maybe related was that after upgrade I had an error that license was not available in Houston but after I forced a license get it worked again.

That is a JupyterLab error which I would think you could resolve by simply reloading the browser page. The JupyterLab front-end is out of sync with the backend because the backend restarted. More info here.

So simple. Thanks for the reply.