No sure what you mean by "off solo". Having the solo switches disengaged is typically the default for most folks. Could be more than one or all tracks are selected and therefore would solo all . Otherwise, if the Ctrl. key is pressed, only one track can be solo'd at a time, same goes for the track mute.
I am using Pro 21 on my desktop, have been editing with Vegas since either 11 or 9 and have never run into this issue before today. All of my audio tracks have, in yellow letters, off(solo) and regardless of deleting, starting a new project, closing and opening, etc...no joy. I have tried all the above suggestions and searched in the Help menu without luck. I will be glad to post screenshots if requested.
You have tacked on to a 7 year old thread that has absolutely nothing to do with your question.
For best results on this peer forum, start a new thread for your unique issue, Vegas version, and equipment configuration, including all of the required information here, Please don't try to compare your observations with the older history on these forums. Thanks:
@jane-f I cannot work out from your screenshots what is causing your problem. Can you upload your project "veg" file somewhere, such as Google Drive, and provide the link so others can download it and have a good look. Don't worry about your source material as we don't need that.