Impossibile to get the xuid

[Sorex]

XUID function or var not working

I am trying to use the admin tool id in the GSC mod. This allows me to easily set ranks to users who have access to extras in the server.
I have tried both guid and xuid. The guid doesn't even convert the value of the admin tool from decimal to hexadecimal.

Regarding the xuid, the function does not give an error, for the game it exists but its return value is 0.
Checking with the command \clientinfo I saw that the id of iw4m matches with the xuid.

I don't know if it's me that's wrong or there's some problem. It may be that I get the variable or function wrong, or it may be a client error.

Update of 11/04/2021

I'll add, I hadn't tested the code on the server side. Apparently the getguid() function only allows me to get the id I'm interested in on the server side. While on the client side I get a completely different result. So it's possible to get the interested id but only on server side