I upgraded the HDD to an SSD and loaded it up with OS Mojave. Secondly I installed another SSD on to the Pcle and loaded OS Catalina on it. Now both SSD are accessible through the Apple logo at the top left corner. I alternate the disks through Preference section. Wifi icon is available on the task bar whenever I choose to work with the disk loaded with Mojave- no problem. However when I swap to the SSD blade that has Catalina on it, there is no Wifi icon and can not connect to the internet until I use wire (Ethernet). On the preference page, I clicked on the network icon but could not see Wifi icon, the wifi icon is there when using Mojave. My problem now is how to get to use wifi with Catalina and not use the Ethernet cable. I would be delighted if I could be put through to solving this problem. I thank you in advance of your ever helpful solution(s).