Error message - "A copy of firefox is already open. Only one copy of firefox can be open at a time" but there is no firefox window open.
Computer crashed suddenly (Macbook Pro). I was able to restart all programs except Firefox. I unistalled and re-downloaded FF, but when I try to open the application, I receive the error "A copy of firefox is already open. Only one copy of firefox can be open at a time". However, there are no other copies of FF open since technically it was uninstalled.
Computer crashed suddenly (Macbook Pro). I was able to restart all programs except Firefox. I unistalled and re-downloaded FF, but when I try to open the application, I receive the error "A copy of firefox is already open. Only one copy of firefox can be open at a time". However, there are no other copies of FF open since technically it was uninstalled.
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uninstall Firefox. Then Delete the Mozilla Firefox Folders in C:\Program Files and C:\Program Files(x86). DO MAC EQUIVALENT Note: your Firefox Profile is saved. But you should make a back up before you do :
- https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles
- https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer
Reinstall with Current Release Firefox 57.0.3 with a Full Version Installer
Please let us know if this solved your issue or if need further assistance.