I have below formula in action hotspot and when I click I got “Cannot execute the specified command”. I want lookup to Title field value, based the value get document id and lauch the attachment.
Your format is incorrect for the OpenDocument @command. OpenDocument with no parameters tries to open the selected document in the view (ui). Check the help for the various parameters and use the one that works best for your needs. Also, I’m not sure if the AttachmentLaunch @command will work the way you want it to here. Particularily if there is more than one attachment. According to the help, the Attachment must be selected when you run this @command.
You might want to look at doing all of this with using LotusScript instead.