Dear Laurie,

the GID of a Probe is stored in the configuration file "PRTG Configuration.dat" on the PRTG Core Server (see How and where does PRTG store its data?). You can open this XML-File with any editor and then simply search for the exact name of the probe, without the content from the brackets "(... Probe on ...)". Please see the following example:

                <name>
                  Local probe
                </name>
                <ownerid>
                  100
                </ownerid>
                <position>
                  10
                </position>
                <priority>
                  3
                </priority>
                <probegid>
                  {E014D5DB-08D9-49BC-8298-AF37EA363F8A}