If you can’t connect Windows and Mac computers
Make sure your Mac is connected to the network. To check your connection, choose Apple menu
> System Preferences, then click Network. Your type of network connection is listed on the left. The indicator next to it should be green.If the computers are supposed to be in the same workgroup and on the same local network or subnetwork, make sure the workgroup name is exactly the same on both.
Make sure you typed the computer names and workgroup name correctly.
Make sure you typed the Mac username and password correctly.
In some cases, you may need to reset the password for the account in Users & Groups preferences. To reset the password, choose Apple menu > System Preferences, then click Users & Groups.
Make sure you typed the Windows username and password correctly.
The password for the Windows user account you are using may need to be changed on the Windows computer.
In some cases, the Windows computer may need to be restarted after the password is changed.
If you are trying to connect to a shared folder on a Mac and see a message that the folder you specified isn’t valid, make sure you entered the information correctly. If the information is entered correctly, check to see whether the Mac is in sleep mode.
If you don’t have access to one or both computers, contact the computer or network administrator for help.
Check Windows Help and Microsoft support services for more information about setting up file sharing on your Windows computer.