Windows service serviceCredentials Invalid hexadecimal string format

Remove all the findValue="XXXXXXX" and after that write it again.. sometimes the invalid char is after findValue="??? <--- here

From Jan Angelovič on MSDN Forum:

If you cut and paste the [Serial Number or Thumbprint] from the common certificate dialog, it is copied in UNICODE (UTF-16LE) encoding with special invisible control characters (0xFF and 0xFE aka “Byte order mark“) on the beginning of the string.

Personally, I saw this with the thumbprint; cut & paste from the dialog into Visual Studio kept 2 non-displayed characters (that could be "stepped through" with the cursor and deleted).