I am trying to upgrade a network license from 2017 to 2021, but when attempting to process the upgrade I am met with an error message that simply says "An error has occurred". It provides no further explanation as to potential reasons, only directs me to make a post in the "Licensing and Installation" forum. For reference, the Licenses and Subscriptions tab under Products and Plans shows me that I have an upgrade available. I am currently using Google Chrome as my browser, but also made an unsuccessful attempt on Microsoft Edge. 

I am looking to find out what is causing this error, and solutions to this so that I can use my available upgrade.