Screen runs same resolution as when it's not running seamless. 1900*1024. I've also tried setting it down. No luck.
If I don't do anything it will eventually disconnect.
The primary computer is showing the screen as screen nr 3. And it's extended.
Just to be clear, this is when you try to initiate a "Seamless Display" connection, you are able to get it to connect but its a black screen, and eventually fails.
If all is true, we would like to get some logs from you. To create them, you will need 'DebugView'
https://learn.microsoft.com/en-us/sysinternals/downloads/debugview
You will as need to create a new Registry key here:
HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Stardock\Multiplicity2\MP\MP\
the key name, type, and value
Name: EnableDebug
type: REG_SZ ('String')
value = 1
Example when done

If you are not comfortable working in the registry, you can use this batch file to create it
https://cdn.stardock.us/support/uploads/Mp4_DebugSwitch.zip
Running it will create it with the correct value. Running it again will turn it off - something you are going to want to do after you have done the collection.
Once complete...
- Close any open applications
- Open the Multiplicity config
- Open Debugview64.exe
- Initiate a Seamless Display connection and allow it to eventually fail (as you said it eventually does with no interaction from you).
- Stop DebugView from collecting

- Save the log out with 'Primary' somewhere in the name.
- The same process should be done on the Secondary but the regkey creation should not be needed as it already outputs debug messages that DebugView can collect.
- Save the logs, zip them together, and upload the zip to a shared drive of your choice (GoogleDrive, DropBox, etc) and post a shared link in a reply
This is a video of the capture process
https://cdn.stardock.us/support/uploads/2024-11-07_13-23-48amcguinness.mp4
Thanks for the help.
Sean Drohan
Stardock Product Lifecycle Manager