I use Meld very frequently and it just started bailing on me today. When I try to run meld from commandline, it stalls for some time and then exits with Failed to register: Timeout was reached.
I did an apt remove, apt update and re-install and the issue is still there.
Any suggestions on debugging this?
For those who hit this issue, try restarting your machine. I found a closed ticket on the meld issue tracker and tried it and sure enough, the issue went away.
Likely there's a meld process that hung in the background and wouldn't quit. Just kill the meld process with SIGTERM (or SIGKILL if SIGTERM doesn't work). No need to restart the machine.