ERROR Database config. Analytics

I'm trying to create a results table with metrics from a customized Key Event in Analytics, but I'm getting the following error:

"Dataset configuration error
Looker Studio cannot connect to your dataset.

Unable to obtain data from the underlying dataset."

Does anyone know how can I fix it? This metric is already part of the database; it's not a custom or calculated field and I don't have the same error with other fields.

Thanks in advance for your help!

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