Hi 英夫岸,

Sorry for the delay in response.

As you have mentioned the error message above, it seems that you get the error when you try to use the Adobe Acrobat Reader DC application.

Please try the troubleshooting steps mentioned in this help link Fatal error - Acrobat failed to connect to a DDE server.

Check if that resolves the issue.

Also, try the troubleshooting steps mentioned below:

1. Check if the application is not open n the task manager:

- Go to the task manager by pressing Ctrl+Alt+Del

- Go to the processes in Task Manager

- End all processes related to Acrobat

- Relaunch the system.

- Launch application again.

2. Repair the installation.

- Go to "Programs and Features" in Control Panel on your system.

- Locate the application name in the list.

- Right click on application name.

- Select Change/Repair from the options.

3. Check the file association on your system.

If you still experience the issue, please let us know the following:

- OS installed on your system

- Exact version of Adobe Acrobat Reader DC. (Take help of the steps mentioned here Identify the product and its version for Acrobat and Reader DC )

Let us know if you need any help.

Regards,

Meenakshi