Account Summary prompt template returns "The LLM response is incorrect"

Title: Agentforce Grid unit – Account Summary prompt template returns "The LLM response is incorrect" 

I'm working on the "Explore Data with Agentforce Grid" unit (Agentforce Grid module) and can't get past the Summary column. 

What happens: 

- The Prompt Template column (Account Summary template, objectToSummarize = @Account) fails on every row with "A temporary system error occurred" or "The LLM response is incorrect. Adjust the instructions and try again." 

- I've tried Update Column, and Setup > Einstein Setup > Reconnect Agents to Salesforce Services, as the unit suggests. 

- I've tried GPT 4 Omni (standard template), GPT 5 and GPT 4.1 (cloned template). Same error each time. 

- It happens in more than one org. 

A "Use AI" column on GPT 5 does work, and a Record Update column writes to Account Description, but the challenge check still says: "We couldn't find any of the Account Description fields updated by the Account Summary grid." 

Is anyone else seeing this? Is there a known issue with the Account Summary prompt template in Agentforce Grid, or a workaround the challenge accepts? 

Thanks!