Chrome don't save password only on the ipad

Question

I have a problem with Google Chrome that is making me crazy: saving my password. As long as the password works fine and store the password in the smart Lock in the following cases:

• Desktop PC with IE, Chrome, Firefox
• MAC with Safari, Firefox and Chrome
• Android with Chrome

But when I try to access the site from iPad2 mini (and other iPads) with Chrome v. 59 Smat Lock does not appear, while for other sites, such as Amazon, Smart Lock works fine and asks me to store the password.

Why is Smart Lock not only active on Chrome for iPad?

N.W.: the site web uses Ajax

<form method="POST" id="idLoginForm" name="form"  data-ng-submit="validate($event)" >
   <fieldset>
        <input  id="USER" class="field__input login--username--background" name="USER" 
                data-ng-change="checkInput(form.USER)" 
                data-ng-focus="usernameFocused()" 
                data-ng-blur="resetFocus()" 
                data-ng-model="data.username" 
                data-ng-required="true">

        <input  name="password" type="password" 
                id="password" 
                data-ng-change="checkInput(form.password)" 
                data-ng-init="usernameFocused(true)" 
                data-ng-focus="passwordFocused()" 
                data-ng-blur="resetFocus()" 
                class="field__input login--password--background"
                data-ng-model="data.password" 
                data-ng-required="true">
    <button data-ng-click="disableButton()"
        data-ng-disabled="isDisabled"
        data-ng-class="{ 'button--disabled': isDisabled}"
        data-ng-attr-type="submit"
        class="button button--block button--login">Accedi</button>
</fieldset>   </form>

Regards,

Gianluigi