Kex_exchange_identification: Connection closed by remote host

I have followed setup tutorial: SSH · Cloudflare Zero Trust docs

It was working yesterday, but this morning it starts to throw error
kex_exchange_identification: Connection closed by remote host
when I try to connect.

weirdly, I didn’t do anything, after some time when i retry ssh myhostname, it opened the browser for authentication, and then I am able to connect. Not sure why there wasn’t any browser opened previously.

And it stopped working again today

ok I think I figure it out, first I have port forwarding opened long time ago, I see a lot of brute force access. Then I migrated local tunnel to remote tunnel. Then was able to successfully connect