Fill & sign does not work when "English with Arabic support" is installed. This is not documented, and there is no feedback to the user - the tool just doesn't do anything.

It took many people painful research to realize that the Arabic support is the problem. See the following thread in Adobe community:

https://community.adobe.com/t5/acrobat-discussions/acrobat-pro-adobe-sign-button-does-not-work-windows-10/m-p/14268784

It seems that Arabic support is installed silently (possibly geo-specific) and causes fill & sign to stop working. It is likely that many users are unaware of this and just can't use fill & sign (a broken feature).

I would ask for two changes:
1. Do not install the Arabic support feature silently. If it is installed based on some criteria, inform the user that it will prevent using fill & sign and let the user opt in or out.
2. When Arabic support is installed and the user tries to use fill & sign, inform the use why it would not work (e.g. a dialog box explaining that this feature is not available when Arabic support is installed).