Hi Dean,
Thanks for reaching out. There isn't a widespread API issue that we can point to related to the access change with your accounts. Is the loss of access specific to the API or have you noticed this in the UI as well? If it's the latter case, I would recommend reaching out to
product support.
If the issue is API specific, can you please reply privately with a sample of customer client IDs with regained access and IDs that are still not accessible?
Thanks,
Matt
Google Ads API Team

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