I'm going to ask LaPastenague......our forum bug exterminator.....to take another look at this thread when he can to offer some suggestions.
In the meantime, there are some things can you can check and/or adjust.
Click on System Preferences (gear icon on the dock)
Open Sharing
Make sure that the name of your Mac appears correctly here, and there is not a (2), (3), (4), etc., after the name. If there is, edit the name so that it appears correctly and close Sharing
While still in System Preferences.....
Open Network
Click on WiFi on the left panel to highlight it, then click Advanced at the lower right of the window
Click the TCP/IP tab
Make sure that the setting for Configure IPv6 is set to Link Local Only
Click OK, then click Apply in the next window
Now highlight Ethernet, and click Advanced
Click TCP/IP
Make sure that the setting for Configure IPv6 is set to Link Local Only
Click OK, then click Apply in the next window
Now go back and click on WiFi again to highlight, and click Advanced
Look at the list of networks to which your Mac has connected and click to highlight the name of any networks that you no longer need
Click the - (minus) button at the bottom of the list to delete that network
Do the same for other networks that you no longer need or want
Close out of System Preferences
Restart the laptop and try to connect again to the wireless network