There is a known issue with ALEKS and the Grammarly browser extension where the answer box disappears when attempting to enter an answer. The current fix is to disable or uninstall Grammarly.

To disable Grammarly click on the link below:
https://support.grammarly.com/hc/en-us/articles/115000091632-Disable-the-Grammarly-browser-extension

To remove Grammarly click on the link below:
https://support.grammarly.com/hc/en-us/articles/115000091591-Uninstall-Grammarly-browser-extension