That formula works only, if everyone of the company who use it would work on the same language in Excel = English.
But unfortunately the FORMULAs in Excel are language-dependend, which I never will understand 
Hence, I only use this formula:
="Last Refresh: "&IFERROR(YEAR(SOP_Refresh_Timestamp)&"-"&TEXT(SOP_Refresh_Timestamp;"MMM")&"-"&DAY(SOP_Refresh_Timestamp)&" "&TEXT(SOP_Refresh_Timestamp;"HH:MM:SS");"Offline")
That will lead independendly of languange settings for example to:
Last Refresh: 2016-Feb-8 12:50:17
Yours
Irmi