error message HTTP Open failed: HTTP Internal Error in transaction /IWFND/GW_CLIENT

[#1]

When I try to run/test OData services.
I have 
error message HTTP Open failed: HTTP Internal Error
or
HTTP Send failed: HTTPIO_PLG_BAD_HANDLE-Fehlermeldung beim Senden der Daten.

[katalin_varga]

To resolve this error, please follow steps outlined in KBA 3562546 - Gateway client shows HTTP Open failed: HTTP Internal Error - SAP for Me