Hi momlo san
Thank you for your reply.
Your understand is correct.
I find its root couse. In SplashTop, I checked [Prevent keyboard and mouse when remote access is established].
The test flow executes [Send keys] action, however remote "computer A" does not accept this action, finally the flow fails to work.
I guess RDP has not this kind of security, so when I access via RDP, the flow works well.
I thank your reply helped me to find this issue.
Many thanks.
Best regards