Solved: Internal Server Error

Hi All

Apologies for the late response - my notifications were lost in the mix with the other mail I receive.
And apologies for the lack of detail in my question. Here are the full details of my issue:

I am working with Dynamics BC, Power Pages/Power Apps to complete this task.
I have set out to create a a customer portal that will give our users access to printed stock they have stored in our warehouse.
Long story short, I opted to create a custom table, 'Customer Item Group' and an API Page to expose the table to the portal being developed in Power Pages.

I've published the API Page to the Dataverse and as result can Read, Insert, Modify and Delete entries in the table and the results of my actions are followed through to BC. I can also view the table and perform the same RIMD actions from the Power Pages 'Data' page.

I can create a list out of the 'Customer Item Group' Dataverse table with no errors BUT when I go to preview the list (as an authenticated user) on the webpage I get the 'Internal Error 500' message. I have set the table permissions so that Authenticated Users and Administrators can view the data. Table access is set to Global since there are no table relations. On further investigation in the console I've found a more elaborate message:

On discovering this I made a few changes, which includes creating a permission set in visual studio code which includes the permissions set:

namespace CIG;
using System.Security.AccessControl;

permissionset 50100 "CIG_Permissions"
{
    IncludedPermissionSets = "D365 BUS FULL ACCESS", "D365 READ", "D365 BASIC";
    Assignable = true;
    Permissions = tabledata "Customer Item Groups" = RIMD,
        tabledata Customer_Item_Group_Code = RIMD,
        table "Customer Item Groups" = X,
        table Customer_Item_Group_Code = X,
        page "API Customer Item Group Code" = X,
        page "API Customer Item Groups" = X,
        page "Customer Item Group Code" = X,
        page "Customer Item Groups" = X;
}

But this didn't help. Here's the code for my table and page respectively:

table 50100 "Customer_Item_Group_Code"
{

    Caption = 'Customer Item Group Code';
    DataCaptionFields = "number", Description;
    DataClassification = CustomerContent;
    Permissions = tabledata Customer_Item_Group_Code = R;

    fields
    {
        field(10; "number"; Code[15])
        {
            Caption = 'No.';
            NotBlank = true;
            DataClassification = CustomerContent;
        }

        field(20; description; Text[30])
        {
            Caption = 'Description';
            DataClassification = CustomerContent;
        }

    }

    keys
    {
        key(PK; "number")
        {
            Clustered = true;
        }
    }

    fieldgroups
    {
        // Add changes to field groups here
        fieldgroup(DropDown; "number", Description) { }
    }

}

API Page

page 50105 "API Customer Item Group Code"
{
    pagetype = API;
    // ApplicationArea = All;
    // UsageCategory = Administration;

    APIVersion = 'v2.0';
    APIPublisher = 'Dataverse';
    APIGroup = 'CustomerItemGroupsVT';

    EntityCaption = 'Customer Item Group Code';
    EntitySetCaption = 'Customer Item Group Codes';
    EntitySetName = 'customerItemGroupCodes';
    EntityName = 'customerItemGroupCode';

    ODataKeyFields = SystemId;
    SourceTable = Customer_Item_Group_Code;
    permissions = tabledata Customer_Item_Group_Code = RIMD;

    Extensible = false;
    DelayedInsert = true;


    layout
    {
        area(Content)
        {

            repeater(Group)
            {

                field(id; Rec.SystemId)
                {
                    Caption = 'Id';
                    Editable = false;
                }
                field(groupNo; Rec."number")
                {
                    Caption = 'No.';
                }

                field(customerNo; Rec.description)
                {
                    Caption = 'Description';
                }
            }
        }
    }
}