Our company's computer have ERROR CODES : (-6000, 83)? I try to Stop Hosting Multi-user access., wh

Hi there Jason,

Sorry to see you're experiencing this error. Stopping multi-user access is certainly one of the solution steps on this so good to see you've tried that.
Which product edition & version and operating system are you using?
There's a couple of KB articles here which contain further troubleshooting which hopefully yields better results -

-6123, 0: Connection to the Accounts Business company file has been lost

Error opening a company file on a QBi network

Error -6177, 0 or -6000, -83 when opening a company file on a network

Let me know how you go