I run my UR10e through TCP/IP(port 30002) by sending a URScript. ThenI tried to control the task by using dashboard port 29999. I’ve succeed in pausing the task and stopping the task, but failed when I tried to replay the paused task where the dashboard socket returns the message failed to execute: play
I wonder why I couldn’t replay my task, because it’s a UR Script string rather than a program file?
I think you’ve answered your own question, because you’re running URScript and not a .urp file, the dashboard server cannot play once paused, I would assume that playing a program from the dashboard server is specifically for a .urp file. Stopping a running process is an easier task programatically than resuming something that was already running
Actually, the Dashboard Server is specifically meant for simple control tasks like play/pause/stop, loading new programs etc.
However, due to safety requirements, the robot needs to be put in Remote Control (see User Manual) to initiate movement. And this needs to be done, before connecting to the Dashboard Server.
Hope it helps 
I ran into a similar problem when I was trying to re-load and re-play a program using the Dashboard Server. What I found was that you need to stop the program before you re- load & play it. Also, if you are using a multi-command request for this, then do it in 2 different commands instead of one. Let the UR controller has some buffer time between stopping and reloading and replaying. That’s how I fixed my problem