Unable to complete Get Started with Sales Email Prompt Templates, I have created the Sales Email Prompt Template. But throwing this issue
I tried almost all solutions mentioned in the comments, for me the following worked:
In properties of the specific Prompt Builder rename Prompt Template Name to Welcome Guest by deleting it and typing it out again. I think Ctrl C + V from somewhere else might have added a different ASCII or spacing. Also changed the model to GPT 5 Mini instead.