Unable to use mobile bank login. Please use website login credentials.

In this case the credentials provided by your client are specifically for a mobile banking site, not their banks' online banking portal, that is accessed via a web browser.

Please ask your client to check their login details are correct by logging in to their banks' online banking portal (not smartphone app). Once the correct login details are in order, your client can return to the link you sent to re-add their bank.

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