sip_chan ERROR

Hi;
I have all the time this error in Asterisk console and I don’t know how can I repair that.
this is the ERROR:
WARNING[5106]: chan_sip.c:12892 handle_response: Remote host can’t match request NOTIFY to call ‘16bd4018299edcf20ff943c562275758@172.20.0.234’. Giving up.

in the adress 172.20.0.234, I install Asterisk and also one softphone.
When I remove that softphone, that WARNING appear

What’s that mean and how I can do to repait that?

Thanks a lot