USB Not reading various hardware when plugged in

Hi, My names Andy, I am a tradesman and not very computer savvy.

I had a issue where our MacBook Air wasn’t reading our iPhones when plugging them in via USB ports, we tried the obvious of different cords and the other USB port with zero luck.

I came across this link from this website

iOS devices connecting and disconnecting rapidly.

Anyway well it worked great for the iPhones but now our computer won’t read the external hard drive or our Garmin biking devices when plugged in via USB. It will charge up the Garmin bike computer but wont recognize it or be able to install new maps etc etc.

I honestly wouldn’t have a clue what to do, I was on the phone to Apple in regards to our external hard drive not being seen by the MacBook (couldn’t mount it) for hours with no luck, they basically said could be the external hard drive itself but old ones booted up with either cords but the one we need to boot up won’t with any cords, but then today I noticed the Garmin issues. So it all just seems too much of a coincidence not to be all related.

Is there anyway this all can be reversed or just fixed to save the headaches its causing.

Your help is very much appreciated.

Andy