I have tried printing a DHL shipping label and am seeing an error returned:

40023: Currency symbol or UNK or could not be found. Please check the currency symbol field. 


The error is being returned because the system is unable to recognize the currency code within the order, or the currency code is set to UNK (Unknown). 

In order to fix it, go to the Edit order tab and amend the currency code manually. Since currency codes are taken from Settings > Countries, you may also wish to update them there for any future orders.