[SOLVED]DHCP server not working

[m-yoshikawa]

Dear all experts,

I am using netpi with firmware virsion V1.2.0.0.
I want to use netpi as a access point with a dhcp server.
Since, I changed netpi's wifi settings as the attached picture.
   
For a short time, it works well.

However, after a particular reboot, the dhcp server does not works.
A client(Windows machine) can connect to netpi through wifi, but no ip adresses are assigned.

It can recover by resetting netpi's wifi configuration by pushing "Save changes" button.
However, after a while, the problem occurs again after a reboot.

For your information, the followings are dnsmasq error messages in syslog. 

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<30>1 2020-06-19T02:46:40+00:00 NTB827EBE916A2 NetworkManager 953 - - dnsmasq: failed to create listening socket for 192.168.205.2: Cannot assign requested address
<26>1 2020-06-19T02:46:40+00:00 NTB827EBE916A2 dnsmasq 1745 - - failed to create listening socket for 192.168.205.2: Cannot assign requested address
<26>1 2020-06-19T02:46:40+00:00 NTB827EBE916A2 dnsmasq 1745 - - FAILED to start up
<4>1 2020-06-19T02:46:40+00:00 NTB827EBE916A2 NetworkManager 953 - - <warn>  [1592534800.5257] dnsmasq[0x22ebcd8]: dnsmasq exited with error: Network access problem (address in use, permissions) (2)

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I want to know the cause of this problem and how can I avoid it.

Best regards.