SOLVED
just enable the grandstream wifi options into ADVANCED/DEFAULT SETTINGS
then
Edit the template file grp2612w.xml
and change like this
<!-- # Access Point 1 -->
<!-- # SSID -->
<!-- # String -->
<!-- Pvalue P8403 -->
{if isset($grandstream_wifi_essid)}
<item name="network.wifi.ap.1.ssid">{$grandstream_wifi_essid}</item>
{/if}
<!-- # Access Point 1 -->
<!-- # Password -->
<!-- # String -->
<!-- Pvalue P8404 -->
{if isset($grandstream_wifi_password)}
<item name="network.wifi.ap.1.password">{$grandstream_wifi_password}</item>
{/if}