You are trying to add a new workspace in your organization in Terraform Cloud, using the same connected VCS (Gitlab) as the one you already have setup, but you get the above error when trying to add it in Firefox (Linux – Ubuntu – 79).
Use Chromi(um) to create the workspace as it works there. You can then use it in Firefox as normal.
You would like to start using Terraform Cloud and when trying to initialize it with the new remote backend (app.terraform.io), you get the following error:
Error: Required token could not be found
Make sure you configured a credentials block for app.terraform.io in your CLI
Follow the instructions here https://www.terraform.io/docs/cloud/free/index.html and create a file ~/.terraformrc (in linux) with an API token.