Actually, just figured it out, at least for me. My Google Sheet was sitting in a Shared Google Drive. And automations don’t support linking to sheets in Shared Drives. I moved the sheet into My Drive and it works fine now.

I’m having the exact same problem with an automation linked to a google form.

+1 for me too. I sincerely hope that limitation isn’t intentional. You don’t limit your product’s features to suit a rigid pricing model, you adapt the pricing model for the software (and the best features for it). Otherwise you won’t be in business ...