pfSense

If the config has additioan DHCP pool with extra parametrs configured, such default-lease-time or max-lease-time, then KEA won't start with out any logs. To fix that need delete from config those extra option. Or just resave affected pool without any changes, it will lead rewrite config without extra options.
For example
<pool>
<range>
<from>192.168.6.2</from>
<to>192.168.6.48</to>
</range>
<descr><![CDATA[NTP Server]]></descr>
<defaultleasetime>600</defaultleasetime>
<maxleasetime>3600</maxleasetime>
After resave it will deleted
<pool>
<range>
<from>192.168.6.2</from>
<to>192.168.6.48</to>
</range>
<descr><![CDATA[NTP Server]]></descr>
<defaultleasetime></defaultleasetime>
<maxleasetime></maxleasetime>