The password was not recognised during Login

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Our clients have been using Sage 50 UK v 24.2 running on Windows Server 2012 for past few years, before 2 days we received this issue on login for one of the Company Dataset, 

Can we resolve this issue, as a Sage Partner, as we have Re-installed the .net Framework and as well as the Application we have removed and installed again, the issue remains on this particular Dataset, the other Company Dataset works fine.