@sanjeev
I overwrite both files but it doesn't work. I did a check on the differences between the old and new (one that you asked to replace) files.
The ticketView.html.twig file seem like no different.
Where the ticket.html.twig different is as shown below:
Comparing files ticket.htmlold.twig and TICKET.HTML.TWIG
***** ticket.htmlold.twig
<span class="uv-icon-channel uv-channel-email"></span> <span>{{ 'Email'|trans }}</span>
{% else %}
<span class="uv-icon-channel uv-channel-web"></span> <span>{{ 'Website'|trans }}</span>
{% endif %}
***** TICKET.HTML.TWIG
<span class="uv-icon-channel uv-channel-email"></span> <span>{{ 'Email'|trans }}</span>
{% elseif ticket.source == 'formbuilder' %}
<span class="uv-icon-channel uv-channel-form"></span> <span>{{ 'Formbuilder'|trans }}</span>
{% else %}
<span class="uv-icon-channel uv-channel-web"></span> <span>{{ 'Website'|trans }}</span>
{% endif %}
***** ticket.htmlold.twig
{% for type in ticketTypeCollection %}
<li data-index="{{ type.id }}"><a href="#">{{ type.description }}</a></li>
{% endfor %}
***** TICKET.HTML.TWIG
{% for type in ticketTypeCollection %}
<li data-index="{{ type.id }}"><a href="#">{{ type.code }}</a></li>
{% endfor %}
***** ticket.htmlold.twig
(<a id="more-tickets-btn" href="{{ path('helpdesk_member_ticket_collection') }}#customer/{{customer
.id}}" target="_blank">{{ '%count% more ticket|%count% more tickets'|transchoice(totalCustomerTickets) }}</a>)
{% endif %}
***** TICKET.HTML.TWIG
(<a id="more-tickets-btn" href="{{ path('helpdesk_member_ticket_collection') }}#customer/{{customer
.id}}" target="_blank">{{ 'count more tickets'|trans({'count': totalCustomerTickets}) }}</a>)
{% endif %}
***** ticket.htmlold.twig
</div>
<div class="uv-element-block">
***** TICKET.HTML.TWIG
</div>
<div class="uv-element-block">
***** ticket.htmlold.twig
<div class="uv-field-block">
<textarea name="reply" id="uv-edit-create-thread" class="uv-field">{{ initialThread.message }}</tex
tarea>
</div>
***** TICKET.HTML.TWIG
<div class="uv-field-block">
{% if initialThread.message|striptags == initialThread.message %}
<textarea name="reply" id="uv-edit-create-thread" class="uv-field">{{ initialThread.message|nl2
br }}</textarea>
%} {% else %}
<textarea name="reply" id="uv-edit-create-thread" class="uv-field">{{ initialThread.message|raw
}}</textarea>
{% endif %}
</div>