Unable to edit text entered into fields in a file I saved

I am using Adobe Reader DC, v2020.013.20064.

After downloading a pdf with fillable fields, I filled most of it out, and saved it. Now I need to go back into the saved pdf and finish filling it out, but all of the fillable fields are locked. When I click on a fillable field, I get a blinking cursor, but I cannot type anything into the field.

* I have not signed the document.

Here are the security settings for this file:

(Edit > Preferences > Security - selected items):
* Enable protected mode at startup
* Protected view: Off
* Enable enhanced security

* Automatically trust sites from my Win OS security zones