AWS EC2 Unable to Change Instance Type

After spinning up a pool of t2.small servers and running some load tests, it became clear I was severely under-powered. Easy enough, I shut down an instance, changed to an m5.large, and started it up again. As usual I opened up a ping to the machine so I could see the second it came back online. I waited. And waited… … OK this isn’t right. What happened? Turns out, Amazon has a special network driver in the form of a kernel module.