2checkout Whmcs MD5 hash failure or unrecognized Currency error

While setting up WHMCS with 2checkout for a client we face both the issues (MD5 Hash Failure and Unrecognized Currency). Customer support from WHMCS and 2checkout was not very helpful, so we troubleshoot ourselves and reach the following solution: MD5 Hash Failure in WHMCS After setting up 2checkout as per whmcs and 2checkout documentation you might face this issue. When you pay the invoice with [...]