I received an email from goDaddy saying my Linux hosting account had been upgraded, I wasn't aware or requeted an upgrade. But since receiving the upgrade the subdomains have stopped working. I have not changed the settings on these at all. I set them up in the Hosting Manager and the records are still there , they have just stopped working
Double check your DNS. If GoDaddy needs to move you for load balancing or because a server is end of life, your IP address will change. The system might not have automatically updated the records for your subdomains.