Create a new api key by unchecking the option "ALM WSAPI Read-only"
Or
Edit the API key and uncheck "ALM WSAPI Read-only"
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Click the link below for more information on CAAgileCentralPlug-In configuration
https://docops.ca.com/ca-continuous-delivery-director/integrations/en/plug-ins/ca-agile-central-plug-in#CAAgileCentralPlug-In-Configuration