I have a mid 2011 21.5 inch iMac (HighSierra 10.13.6) and it has been disconnecting from the wifi constantly. Like every half and hour or so. Turning on and off the wifi does not fix the problem. It also does not immediately reconnect to my wifi. I either have to restart the whole system, or set up a personal hotspot, connect to that, then choose and connect to the wifi. I live in an apartment complex and the modem is not in my unit so I can't restart it or anything. Also, all my other devices have no problem (iphone, ipad, ps4,etc.) They connect and stay connected. The problem did go away for a while, but it has started again. No idea what changed or if I did anything. Any idea what's causing this? I have renewed the DHCP Lease but it did not do a thing.