The same happened to me, I am using the 64-bit version of Google Chrome 75.0.3770.142 on Windows 10. I resolve the issue by trashing all browser data e.g., cookies, etc. You can find the steps to remove that data here.
Even after all those steps if your problem does not resolve then use the following ways and it will definitely work:-
Close and reopen the browser.
Cry quietly to me and question my decisions in life.
The Lambda editor in the console is AWS Cloud9, which needs some stuff (e.g., cookies) that are spelt out here.