(TLDR for solution: downloaded 2021.2.3, changed from key press to mouse click which allows use of the textbox for responses, and removed html from the experiment settings to allow successful upload.)
Thank you both so much for your replies!
2021.2.3 won’t run locally on my main computer (although older versions wouldn’t either - here is my topic about that), so I am using the older install of 2021.1.2 on another computer to do most of the coding.
I downloaded 2021.2.3 to my main computer again and began trying to make changes as suggested, starting by changing the key press for a mouse click. However, this spawns another error: the upload will not load any resources, and does not even appear to be trying to.
This does not change when I clear my cookies or change browsers, and also doesn’t change when I set all of the resources to preload in PsychoPy using the settings > online tab. Once you click okay, the experiment crashes upon trying to load the first resource. This bug has been reported a few times: 1 2 3.
As far as fixing this issue, I tried recreating without html and then doing a clean upload of the experiment (duplicated the whole experiment folder and PsychoPy file and uploaded from that). Everything is now working when I upload online, including the mouse click to successfully type in the textbox. The experiment still won’t run locally but the main issue is fixed : )
Thank you both so much again!