I have callouts that use a
Named Credential and a
Custom Oauth2 Auth Provider fail with this error response:
Invalid parameter value "[hidden]" for parameter "Decryption Exception"
A similar error is sometimes shown when I resave the Named Credential
Unable to Access Page The value of the "Decryption Exception" parameter contains a character that is not allowed or the value exceeds the maximum allowed length. Remove the character from the parameter value or reduce the value length and resubmit. If the error still persists, report it to our Customer Support team. Provide the URL of the page you were requesting as well as any other related information.
When I simulate the Oauth Flow and Callout in Postman it always works. I'm quite sure this is a Platform bug.