Resolved.
Instruction:
On vendor/uvdesk/support-center-bundle/Resources/views/Knowledgebase/ticket.html.twig
Open ticket.html.twig
find the line (98):
<button type="submit" id="create-ticket-btn" class="uv-btn">{{ 'Create Ticket'|trans }}</button>
in the row before you will find (97):
<div class="uv-element-block">
before that line add on line (96):
<div class="clearfix"></div>
<div class="g-recaptcha" data-sitekey="YOUR SITE KEY"></div>
<div class="clearfix"></div>
now find some rows below in the script check (153)
'reply' : {
required : true,
msg : '{{ "This field is mandatory"|trans }}'
},
after that add (on line 154):
'g-recaptcha-response' : {
fn: function(value) {
if(grecaptcha.getResponse().length > 0)
return false;
else
return true;
},
msg : 'Please select CAPTCHA'
}
save and clean cache.
This will work only for ticket page, for protect login page I have no idea.