403 with rest api call

I;ve seen a few other people with this issue, and some where resolved, but nowhere is a solution to be found.

The code:

$VLANNAAM = "Somevlan"

$cred = get-credential

$invoked = Invoke-RestMethod -Uri ("https://"+$Hostname+":17778/SolarWinds/InformationService/v3/Json/Query?query=SELECT GroupId,VLAN_Naam FROM IPAM.GroupNodeAttr WHERE (VLAN_Naam='$VLANNAAM')") -method Get -credential $cred

For the credentials I've used a windows account, local account, database user.

Nothing works, Always the 403 error.