Data are not saved in ComboBox

Hi community,

I installed the multichoice package from the marketplace and I created a combobox but for some reason I'm not able to save the data once I filled the created combobox.

Here is my schema :

define("MTF_Candidat1Page", ["MultiChoiceMixin"], function() {
	return {
		entitySchemaName: "MTF_Candidat",
		attributes: {
			"UsrComboBox": {
				"dataValueType": Terrasoft.DataValueType.LOOKUP
			},
		},
		mixins: {
			MultiChoiceMixin: "Terrasoft.MultiChoiceMixin"
		},
		methods: {
			init: function() {
				this.callParent(arguments);
				this.mixins.MultiChoiceMixin.init.call(this, arguments);
			},
			getMultiChoiceEntitiesConfig: function() {
				items = {
					UsrComboBox: {
						mainEntitySchemaName: "MTF_Candidat",
						mainColumnName: "Lkp_Francais",
						relatedEntitySchemaName: "MTFcompetenceslinguistiques",
						relatedColumnName: "Name"
					}
				};
				return items;
			}
		},
		...
		diff: /**SCHEMA_DIFF*/[
		...
		{
				"operation": "insert",
				"parentName": "TabMTFInfosCandidatTabLabelGridLayoutd7450211",
				"propertyName": "items",
				"name": "UsrComboBox",
				"values": {
					"className": "Terrasoft.MultiChoiceCombobox",
					"layout": {
						"colSpan": 12,
						"rowSpan": 2,
						"column": 0,
						"row": 0,
						"layoutName": "TabMTFInfosCandidatTabLabelGridLayoutd7450211"
					},
					"bindTo": "UsrComboBox",
					"dataValueType": Terrasoft.DataValueType.ENUM,
					"labelConfig": {
						"caption": "Test ComboBox"
					}
				},
				
			},
		...
		]/**SCHEMA_DIFF*/
	};
});

"UsrComboBox" is an attribute I created in the attributes of this schema.

"MTF_Candidat" is an object that I created in the page wizard.

"Lkp_Francais" is the field ID for a lookup already defined in the page wizard. By default when I created Lkp_Francais, the connected lookup is "MTFcompetenceslinguistiques".

"MTFcompetenceslinguistiques" is a basic lookup with only the inherited fields

It produces this combobox :

The UI part it works fine :

But if I save my object, close it and reopen it, the data previously filled in the combobox are no longer there:

I tried to generate the source code for all the modified schemas in the advanced settings, then I recompiled everything and it still doesn't work.

Do you have any idea what is going on and what I can do to solve this problem?

EDIT : in my getMultiChoiceEntitiesConfig method I tried to change

mainColumnName: "Lkp_Francais"

to

mainColumnName: "Id"

as recommanded in https://marketplace.creatio.com/app/multiple-choice-field-setup-creatio under the installation part and this time when I save my object it just load indefinitely. I tried to change it to "MTFContactCandidat" which is a lookup connected to a Contact object and the result was the same,when I click on save it loads indefinitely.

Best regards,

Julien G.