[Notes]: - It seems that the "accessibility.force_disabled" integer pref is changed to "1" value after closing the tab. [Affected versions]: - Nightly 59.0a1 (2018-01-05) try build [Affected Platforms]: - All Windows - All Mac - All Linux [Prerequisites]: - Have the latest try build 59.0a1 from (2018-01-05) installed. - Accessibility feature is checked in "Toolbox Options". [Steps to reproduce]: 1. Open the Nightly try build with the profile from prerequisites. 2. Navigate to any website press the "F12" key and click the "Accessibility" tab. 3. Click the "Enable Accessibility Features" button. 4. Open a new tab and navigate to the same website. 5. Press "F12" key and close the tab. 6. Open another tab and navigate to a different website. 7. Press "F12" key and observe the Accessibility tab. [Expected Results]: - The Accessibility feature can be enabled. [Actual Results]: - The "Enable Accessibility Features" button is grayed out and the feature can not be enabled. [Additional Notes]: - Even if the browser is restarted the issue is still reproducible. - Attaching a screen recording with the issue.

This issue is no longer reproducible on latest Nightly try build. I will close this issue as Resolved-Worksforme.