I don't know what to take a screenshot of. My guildmates tell me something should be there, and nothing is.
Have them take a screenshot of when they expect something to be there, where nothing is.
And in particular, I'm confused about the whole
"GP: XXX (itemlvl=xx itemvalue=xxx]"
I think the number that they are getting there is from the EPGP mod (which you don't have installed, but which your members who are reporting this probably do), as the GRSS doesn't generate any text like that.
In the GRSS, when you run the GetGRSSDKP.exe program, that program will download the latest Standings, as well as the item prices set in your system currently. Then, when an item has been received, the value of the loot will be automatically in the box (remember, that is ONLY if you have the values preset in your website).
In the EPGP mod (which is not a mod we support), item prices are determined formulaicly by the slot (hands, feet, chest, etc) and the level of the item.
This is why I believe your members have the EPGP mod running, and why you're not getting the textual display you're expecting.