Unable to connect to wifi, OS 10.11.6, and failure to recognize when a hotspot network is joined

I am recently unable to connect to my wifi AP from my mini which runs OS 10.11.6. There seems to be nothing changed about the AP, since other clients have no trouble connecting.

Last week my mini began dropping the wifi connection after brief periods of inactivity, which was annoying, but now, connecting at all would be a positive.

Signal strength of homenet is -58 dBm, which should be sufficient, and my wifi chipset finds my network and assigns it the icon indicating the strongest signal strength.

I ran the wifi diagnostics, and here are some lines that are perhaps relevant:

Mon Dec 12 02:22:53.900 <kernel> Unexpected payload found for message 9, dataLen 0
Mon Dec 12 02:22:53.900 <kernel> No networks found. Please check if the network exists and is in range
Mon Dec 12 02:22:53.943 <kernel> en1: Terminating supplicant.
Mon Dec 12 02:22:53.943 <kernel> RSNSupplicant: Releasing authenticator for 00:00:00:00:00:00
Mon Dec 12 02:22:53.943 Info: <airportd[65]> <en1> Failed to associate to Wi-Fi network homenet, returned error code -3905, retrying
Mon Dec 12 02:22:54.172 Info: <airportd[65]> Failed to associate to Wi-Fi network homenet on interface en1, returned error code -3905
Mon Dec 12 02:22:54.172 Info: <airportd[65]> __73-[CWXPCInterfaceContext manageProblematicNetworks:addProblematic:reason:]_block_invoke: null profile
Mon Dec 12 02:22:54.174 <airportd[65]> _SC_callback: Changed keys = { 'State:/Network/Interface/en1/AirPort/Power Status' 'State:/Network/Interface/en1/AirPort/AirPlay' }
Mon Dec 12 02:22:54.174 SC: <airportd[65]> airportdProcessSystemConfigurationEvent: Processing 'State:/Network/Interface/en1/AirPort/Power Status'
Mon Dec 12 02:22:54.174 SC: <airportd[65]> airportdProcessSystemConfigurationEvent: Processing 'State:/Network/Interface/en1/AirPort/AirPlay'
Mon Dec 12 02:22:54.174 <airportd[65]> _SC_callback: Changed keys = { 'State:/Network/Interface/en1/AirPort/CHANNEL' }
Mon Dec 12 02:22:54.174 SC: <airportd[65]> airportdProcessSystemConfigurationEvent: Processing 'State:/Network/Interface/en1/AirPort/CHANNEL'
Mon Dec 12 02:22:54.174 AutoJoin: <airportd[65]> -[CWXPCSubsystem __associateToWiFiNetwork:tetherDevice:password:is8021X:passpointDomain:remember:updateUserKeychain:interface:error:]: Failed to associate to Wi-Fi network homenet on interface en1, triggering auto-join in 10 seconds.
Mon Dec 12 02:22:54.174 AutoJoin: <airportd[65]> -[CWXPCInterfaceContext __scheduleAutoJoinRetryWithInterval:]: Auto-join will retry in 11.000000 seconds.
Mon Dec 12 02:22:54.175 Info: <airportd[65]> -[CWXPCSubsystem associateToWiFiNetwork:password:is8021X:remember:interfaceName:authorization:connection:error:]: Association failed for network <686f6d64 6c79> on interface en1, returned error Error Domain=com.apple.wifi.apple80211API.error Code=-3905 "(null)"
Mon Dec 12 02:22:54.175 <airportd[65]> _SC_callback: Changed keys = { 'State:/Network/Interface/en1/AirPort/AutoJoinTimestamp' }
Mon Dec 12 02:22:54.175 Info: <airportd[65]> -[CWXPCSubsystem __submitAssociationFailureMetric:error:]: assoc. failure metric data: CWAWDMetricAssociationFailureData: oui: 00:21:29, channel: 1, rssi: -58, error: -3905, reason: 0, securityDesc: WPA 
Mon Dec 12 02:22:54.175 SC: <airportd[65]> airportdProcessSystemConfigurationEvent: Processing 'State:/Network/Interface/en1/AirPort/AutoJoinTimestamp'

I am using the correct wifi password, and the MAC address is whitelisted on the AP.

On the advice of another with a similar problem, I disabled AirDrop.

Things that suggest this is Mac s/w related: 1. The mac is openly refusing to join the wifi network, which it finds and recognizes, and joined until recently. 2. When I use my iphone's hotspot as a network, I get the same error dialog "The network could not be joined" even though it IS joined and works fine. After connecting to it the Mac doesn't draw the "chain-links" connection icon in place of the greyed out wifi icon. So the Mac displays no connection, but there is a connection that works for the browser and the terminal window. It suggests that my whole network connection package is messed up.

Any ideas? What is the significance of error "3905?"