Has the AdBlock button vanished from the browser toolbar every time you open Firefox? Visit about://addons and see whether AdBlock has been disabled or even uninstalled. Either way, it could be an issue with malware, an extension that doesn't like AdBlock, a broken installation of AdBlock, or even Firefox itself.
Look for malware
If AdBlock is constantly being uninstalled or disabled every time you open Firefox, it could mean your computer is infected with malware—even if you have a Mac. Macs are vulnerable to malware just as Windows computers are, it's just more rare. Malware often looks for and uninstalls extensions that can keep them from doing their nefarious work.
The first thing you should do is check about://addons for any extensions you don't remember installing yourself. If you find any, remove them.
Next, scan your computer with an anti-malware application. We recommend Malwarebytes. We are not affiliated with them; we've just found that their software tends to find malware that others miss. Plus, it's available for both Windows and MacOS, and it's free!
If the scan finds malware, follow the instructions in this Knowledge Base article.
Look for extensions that don't play well with others
If AdBlock is still being disabled or uninstalled when you open Firefox, look for extensions that don't want you to use ad blockers.
- Reinstall AdBlock.
- Disable all other extensions except for AdBlock.
- Restart Firefox a few times. If AdBlock is still there each time, it means one of the extensions you disabled is the culprit.
- Enable each of the other extensions one at a time, restarting Firefox after each one, until AdBlock is uninstalled or disabled again. The last extension you enabled is the jealous one.
You'll need to decide which extension you value more, that one or AdBlock. If you like them both, just re-enable AdBlock every time you start Firefox. You can also be a good web citizen by reporting the problem to the developer of the other extension.
Extensions can become corrupted if something goes wrong in Firefox. Try reinstalling AdBlock. Be sure to copy any custom filters to a text file for safekeeping first.
By the way, our payment page opens every time AdBlock is installed. If you don't want to pay for AdBlock at this time, just close the page.
Try some Firefox troubleshooting
If the above suggestions haven't helped, the culprit may be Firefox itself. Your profile or the file that stores the extensions registry might have become corrupted. Try this solution first. If that doesn't help, try these troubleshooting steps.