I've also had a similar problem where my Raspberry Pi is not connecting to HDMI. I have tried an article but have had not luck. If I reformat my microSD will the HDMI problem be fixed? (It may be running NOOBS or Raspbian but I am not not sure and it is a NOOBS card from 2015)

Or should I just but a new SD?

@Roxiun If you have a 2015 OS it will not run on a PI3B+ (which was released in March 2018)

Sorry it's a Pi 3 Model B

I have updated the software. Can I reformat the microSD to solve the HDMI issue?

Or should I buy a new microSD

Yeah the software was originally 2016 although it has been updated in the past few months