Hi Andrii,
The code is still failing to "fire"?
function OnCrmPageLoad() {
    Xrm.Page.getControl("header_process_ro_hiddengateway2approvedtoproceed").setVisible(false);
    Tier1();
    Tier2();
    Tier3();
    Tier4();
    ApprovalGateway2ReadOnly()
    }
//Tier 1 Copy Approval User & Time
function Tier1() {
    var approvalstatus = Xrm.Page.getAttribute("ro_tier1approval").getValue()
    if (approvalstatus === "1" || approvalstatus === "2") {
        var setUservalue = new Array();
        setUservalue[0] = new Object();
        setUservalue[0].id = Xrm.Page.context.getUserId();
        setUservalue[0].entityType = 'systemuser';
        setUservalue[0].name = Xrm.Page.context.getUserName();
        Xrm.Page.getAttribute("ro_decisionbyteir1gateway2").setValue(setUservalue)
        var currentdate = new Date();
        Xrm.Page.data.entity.attributes.get("ro_tdecisiondateteir1gateway2").setValue(currentdate);
    }
}
//Tier 2 Copy Approval User & Time
function Tier2() {
    var approvalstatus = Xrm.Page.getAttribute("ro_tier2gateway2apporvalby").getValue()
    if (approvalstatus === "1" || approvalstatus === "2") {
        var setUservalue = new Array();
        setUservalue[0] = new Object();
        setUservalue[0].id = Xrm.Page.context.getUserId();
        setUservalue[0].entityType = 'systemuser';
        setUservalue[0].name = Xrm.Page.context.getUserName();
        Xrm.Page.getAttribute("ro_decisionbyteir2gateway2").setValue(setUservalue)
        var currentdate = new Date();
        Xrm.Page.data.entity.attributes.get("ro_decisiondateteir2gateway2").setValue(currentdate);
    }
}
//Tier 3 Copy Approval User & Time
function Tier3() {
    var approvalstatus = Xrm.Page.getAttribute("ro_tier3approvalgateway2").getValue()
    if (approvalstatus === "1" || approvalstatus === "2") {
        var setUservalue = new Array();
        setUservalue[0] = new Object();
        setUservalue[0].id = Xrm.Page.context.getUserId();
        setUservalue[0].entityType = 'systemuser';
        setUservalue[0].name = Xrm.Page.context.getUserName();
        Xrm.Page.getAttribute("ro_decisionbyteir3gateway2").setValue(setUservalue)
        var currentdate = new Date();
        Xrm.Page.data.entity.attributes.get("ro_decisiondateteir3gateway2").setValue(currentdate);
    }
}
//Tier 4 Copy Approval User & Time
function Tier4() {
    var approvalstatus = Xrm.Page.getAttribute("ro_tier4approvalgateway2").getValue()
    if (approvalstatus === "1" || approvalstatus === "2") {
        var setUservalue = new Array();
        setUservalue[0] = new Object();
        setUservalue[0].id = Xrm.Page.context.getUserId();
        setUservalue[0].entityType = 'systemuser';
        setUservalue[0].name = Xrm.Page.context.getUserName();
        Xrm.Page.getAttribute("ro_decisionbyteir4gateway2").setValue(setUservalue)
        var currentdate = new Date();
        Xrm.Page.data.entity.attributes.get("ro_decisiondateteir4gateway2").setValue(currentdate);
    }
}
//Gateway 2 Set Approval 
function approvedtoproceed() {
    var Tier2 = Xrm.Page.getAttribute("ro_tier2gateway2apporvalby").getValue()
    var Tier3 = Xrm.Page.getAttribute("ro_tier3approvalgateway2").getValue()
    var Tier4 = Xrm.Page.getAttribute("ro_tier4approvalgateway2").getValue()
    var approvalstatus = Xrm.Page.getAttribute("ro_tier1approval").getValue()
    var estimatedvalue = Xrm.Page.getAttribute("estimatedvalue").getValue()
    if (approvalstatus == 1 && Tier2 == 1 && estimatedvalue < 4999999) {
        Xrm.Page.getAttribute("ro_hiddengateway2approvedtoproceed").setValue(1);
        return;
    }
    if (approvalstatus == 1 && Tier3 == 1 && Tier2 == 1 && estimatedvalue < 7499999) {
        Xrm.Page.getAttribute("ro_hiddengateway2approvedtoproceed").setValue(1);
        return;
    }
    if (approvalstatus == 1 && Tier3 == 1 && Tier2 == 1 && estimatedvalue > 7499999 && Tier4 == 1) {
        Xrm.Page.getAttribute("ro_hiddengateway2approvedtoproceed").setValue(1);
        return;
    }
    Xrm.Page.getAttribute("ro_hiddengateway2approvedtoproceed").setValue(0);
}
//Set Ready only once approved or rejected
function ApprovalGateway2ReadOnly() {
    var Tier1 = Xrm.Page.getAttribute("ro_tier1approval").getValue()
    if (Tier1 === "1" || Tier1 === "2") {
        Xrm.Page.ui.controls.get("ro_decisionbyteir1gateway2").setDisabled(true)
        Xrm.Page.ui.controls.get("ro_tdecisiondateteir1gateway2").setDisabled(true)
    }
    else {
        Xrm.Page.ui.controls.get("ro_decisionbyteir1gateway2").setDisabled(false)
        Xrm.Page.ui.controls.get("ro_tdecisiondateteir1gateway2").setDisabled(false)
    }
    var Tier2 = Xrm.Page.getAttribute("ro_tier2gateway2apporvalby").getValue()
    if (Tier2 === "1" || Tier2 === "2") {
        Xrm.Page.ui.controls.get("ro_decisionbyteir2gateway2").setDisabled(true)
        Xrm.Page.ui.controls.get("ro_decisiondateteir2gateway2").setDisabled(true)
    }
    else {
        Xrm.Page.ui.controls.get("ro_decisionbyteir2gateway2").setDisabled(false)
        Xrm.Page.ui.controls.get("ro_decisiondateteir2gateway2").setDisabled(false)
    }
    var Tier3 = Xrm.Page.getAttribute("ro_tier3approvalgateway2").getValue()
    if (Tier3 === "1" || Tier3 === "2") {
        Xrm.Page.ui.controls.get("ro_decisionbyteir3gateway2").setDisabled(true)
        Xrm.Page.ui.controls.get("ro_decisiondateteir3gateway2").setDisabled(true)
    }
    else {
        Xrm.Page.ui.controls.get("ro_decisionbyteir3gateway2").setDisabled(false)
        Xrm.Page.ui.controls.get("ro_decisiondateteir3gateway2").setDisabled(false)
    }
    var Tier4 = Xrm.Page.getAttribute("ro_tier4approvalgateway2").getValue()
    if (Tier4 === "1" || Tier4 === "2") {
        Xrm.Page.ui.controls.get("ro_decisionbyteir4gateway2").setDisabled(true)
        Xrm.Page.ui.controls.get("ro_decisiondateteir4gateway2").setDisabled(true)
    }
    else {
        Xrm.Page.ui.controls.get("ro_decisionbyteir4gateway2").setDisabled(false)
        Xrm.Page.ui.controls.get("ro_decisiondateteir4gateway2").setDisabled(false)
    }
}