no error message when upload amount is exceeded

Dear team,

in my contact form there is a possibility to upload max. 10 pictures. In total they should not exceed 10 MB. If this happens now, unfortunately, no error message appears and the form is not sent.
In the backend the form looks like this:

<h3>Supporting Material*</h3>
<p>Please provide a minimum of 3 images (maxium 10). Only jpeg and png allowed (<b>max. upload size: 10MB <u>total</u></b>).
</p>
<div class=”wps-form-column”>
<label>[mfile* upload-file-824 filetypes:jpeg|jpg|png|zip max-file:10 limit:10000000b]</label>
</div>

Can you help?
Kind regards,
Anna

The page I need help with: [log in to see the link]