[Vuejs]-Vee-validate 3 and Bootstrap 3 form error styling

You have a typo, "lenght" instead of "length", and the " > 0" is not mandatory.
The first example should be ok.

<ValidationProvider v-slot="{ errors }">
    <div class="form-group" :class="{'has-error': errors.length}">
        <label for="credit-card">
            Card Number
        </label>
        <input type="text" id="credit-card" class="form-control" data-stripe="number" v-model="paymentForm.creditCard.number"/>
    </div>
</ValidationProvider>