tab key won't focus on a button
I have an applet that needs to be accessible, so the user must be able to use it with keyboard only - no mouse. I have an input box and a button. Using the TAB key when in the applet in desktop GGB 5 works perfectly. But, when I upload it to geogebra.org, only the input box gets focus and I can't tab over to the button.
I've attached the GGB 5 file that should work well, and you can find the online version here: https://www.geogebra.org/m/fdfnbney
Any thoughts on a solution?
(BTW, I originally had a checkbox for help, but that wouldn't get focus either. I thought that changing the textbox to a button would help, but it didn't