The code listed in the error message ("X") is an analysis code. The error means that the currency selected on that analysis code does not match the currency on the supplier you are using - however the error can also appear if the analysis code does not exist at all.
Firstly, please check you have completed all relevant fields on the detail line of the request. If the error features a code such as 01-123 and your analysis codes in Access Financials are usually 01-123-1234, this indicates that a field has not been completed on the detail line.
If all fields have been completed, please check the analysis code in the error message in Access Financials to ensure it is correct and is set with the correct currency code.
To check this:
Log in to Access Financials
Click Creditors, Settings and analysis
Find and select the analysis code that was listed in the error message.
If it does not exist, you will need to create it and this should resolve the problem.
If it does exist, make a note of the currency it is set to use.
Click Creditors, Suppliers
Find and select the supplier you are using.
Ensure that they are using the same currency as the analysis code. If they are not, then you will need to change whichever one is wrong - the Supplier or the Analysis code. Once the currency on both the Analysis code and the Supplier match, the error will no longer appear.