'Unable to send transaction - Unable to calculate fee for delegated transfer: HTTP 451' error displayed when trying to send assets in Channels app, resulting in no option to complete a transaction.
Generally, HTTP 451 is the error status code of the HTTP protocol displayed when access to a resource which cannot be served for legal reasons is requested. For example, access to a web page censored by a local governmental authority.
In Channels app, the error is caused by lack of Know-Your-Customer (KYC) verification, which is the legal reason for a transaction to be denied by the system. This can happen due to one of the following reasons:
Check the status of your KYC verification in the app:
To eliminate the cause of the error, complete the next available tier of KYC.
Once done, re-check the verification status.
The below screenshot is an example of upgrading KYC Tier 0 to KYC Tier 1