Mobile Approval Failed for specific user

Summary:

We have a user experiencing an issue when he tried to approve using a keyword, we have verified his response its correct, first line , no blank spaces, but CPQ still returning an email saying action not found w that keyword, see below message.

"An error has occurred while trying to process your Request. No changes have been saved. Details of the error are:

No action could be found having the keyword 'Accept'."

Our workflow has multiple approvers, and other users are able to approve via keyword, anyone has experienced a similar issue?, what I could be missing?

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