Why can I not select items to bulk edit them?

If you are not able to select items in your Podio, it means that you are a Guest, Light or Regular member in that workspace.

Ask your organization admin to change your member role to Admin.

For info on member roles, you can read this article from the Podio help centre: https://help.podio.com/hc/en-us/articles/201019898-Member-roles-in-workspaces