I can ping to jetson 192.168.55.1, I can ssh from jetson to PC, but I CAN NOT ssh from PC to Jetson.
This is a message

connection reset by 192.168.55.1 port 22
I tried with different PC and the error is same. Please help me.
How to Fix The "Connection reset by peer" SSH Error
  
This article helps identify the cause of the "ssh_exchange_identification: read: Connection reset by peer" error and fix your connection fast.
    Est. reading time: 11 minutes
              
@DaveYYY

Thanks for response.

I tried your methods and many recommends but it did not work.

I reflashed again and the error is solved.

From my experience of working with Jetson Xavier NX. There are “some problems” with flashing Jetson Xavier NX with SDK manager.  It is not stable to flash and sometimes we need to trick to workaround it.
              
Something to always test if you cannot ssh from outside of a system to inside: Try ssh from the local computer to itself. Example:

ssh 127.0.0.1