The router connection failed to connect to openwisp!

[os ks]

1.The openwisp-config configuration on the router client is as follows:

config controller 'http'
        option url 'https://47.115.140.113'
        option interval '120'
        option management_interval '10'
        option registration_interval '30'
        option verify_ssl '0'
        option shared_secret 'daEhzlCbylxvgBP3JGFeSfXKCOuO8kRl'
        #option consistent_key '1'
        #option mac_interface 'eth0'
        #option management_interface 'tun0'
        #option merge_config '1'
        #option tags ''
        #option test_config '1'
        #option test_script '/usr/sbin/mytest'
        #option hardware_id_script '/usr/sbin/read_hw_id'
        #option hardware_id_key '1'
        #option bootup_delay '0'
        #option uuid ''
        #option key ''
        # curl options
        #option connect_timeout '15'
        #option max_time '30'
        option capath '/etc/ssl/certs'
        option cacert '/etc/ssl/certs/ca-certificates.crt'
        #option checksum_max_retries '5'
        #option checksum_retry_delay '6'
        # hooks
        #option pre_reload_hook '/usr/sbin/my_pre_reload_hook'
        #option post_reload_hook '/usr/sbin/my_post_reload_hook'

2.The router prints openwisp logs in the background as follows：

Registration failed! Unrecognized or unsupported SSH key algorithm, only RSA and ED25519 are currently supported.

3.The ssh certificate configuration on the server background is as follows:

root@iZwz958d59mh3hd1vt9324Z:~/.ssh# ls
id_ed25519  id_ed25519.pub  known_hosts  known_hosts.old

Please give advice to give a solution!