Did you go through the troubleshooting steps from the VSCode Marketplace page?
The following steps are good standard troubleshooting, as well as troubleshooting "Error ##15 Can't initialize target."
- Make sure the ESTK stand-alone application is closed
- Close the target application (example: Photoshop)
- Close Visual Studio Code
- Make sure there are no VS "Code Helper" processes in the Activity Monitor (Mac) or Task Manager (Windows)
- Restart Visual Studio Code
- Does it work then?
- If not, does a reboot help?
I've also found updating VSCode helps.
As for continuing to run ESTK (on macOS) into the near-term future while we wait for the VSCode Plugin to be open-sourced and more robust, and/or for UXP to replace CEP, here are some options:
- Create a partition running Mojave
- Bootcamp your mac & install Windows on a partition
- Try https://www.macincloud.com/
- Try a Windows VM
- Try Parallels' Bootcamp: https://www.parallels.com (no restarts)
- Upgrade a VM to run older MacOS versions