Hi,
Try to enter the ddns address via SSH or CLI (https://wiki.teltonika.lt/view/CLI) directly in configuration file.
To edit configuration, enter command:
vi /etc/config/rs
You will get similar information:
config rs232 'rs232'
option debug '0'
option ip_listen ' '
option ntrip_nmea '$GPGGA,123519,5925.150,N,02443.300,E,1,08,0.9,0.0,M,0
option databits '8'
option parity 'none'
option stopbits '2'
option flowcontrol 'none'
option type 'ntrip'
option ntrip_data_format 'n'
option enabled '1'
option baudrate '9600'
option ntrip_ip 'teltonika.no-ip.com'
option ntrip_port '60'
option ntrip_mount_point '12'
option ntrip_user 'test'
option ntrip_password 'test'
config rs485 'rs485'
option enabled '0'
option debug '0'
option ip_listen ' '
To enter into edit mode in VI editor press i.
Under config rs232 'rs232' option ntrip_ip change IP address '0.0.0.0' to ddns address 'afasfxxxxxxx.myfritz.net'
To exit edit mode press "Esc" button and to leave VI editor with safe, enter :wq and press "Enter". Enter luci-reload to restart service.