btcpayserver/BTCPayServer/Views/UIPublic/PayButtonHandle.cshtml

@{ 
    var allErrors = ViewData.ModelState.Values.SelectMany(v => v.Errors.Select(b => b.ErrorMessage));
}


<div class="row">
    <div class="col-lg-12">
        <h2>Pay Button request failed</h2>
        Please fix following errors:
        <ul>
            @foreach (var error in allErrors)
            {
                <li>@error</li>
            }
        </ul>
    </div>
</div>