Hi meadowmt. 

Thanks for stopping by this afternoon, I'm happy to shed some light on what's going on. It sounds like the issue is occurring when you're switching the host computer from Multi-User mode to Single-User mode. This is because the Host computer puts out a signal for your second computer to work off of. When you break that line, the only way to get it back is to restart the program hence why it's working when you close QuickBooks and reopen it. I;m attaching an image below that represents the connection between the Hosting device and the secondary workstation to better illustrate what I'm referring too. 

Unfortunately there's no way around this as QuickBooks Desktop is internally based, If you want to be able to access your QuickBooks products on multiple platforms and different times then our cloud based storage system utilized with QuickBooks Online may be a direction you would want to explore. 

There's a couple more pieces of information you may find insightful on hosting and multi-user mode in QuickBooks Desktop I'm sharing below:

• Hosting your company data in multi-user mode in QuickBooks Desktop.
• How to fix hosting errors. 

If you have any other questions or concerns, feel free to post them here. Thank you for your time and have a nice afternoon.