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Unable to launch Firefox after update install to version 98.0.2

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I have an iMac that is a decade old. Running macOS High Sierra version 10.13.6 That is as updated as I can get on this processor.

I had a normal "there is a newer version of Firefox available" update alert, so relaunched Firefox to update. So on Monday 4th April NZ time i got the update. As usual I got the message [in a dialogue box]: Close Firefox. A copy of Firefox is already open. Only one copy of Firefox can be open at a time.

So far, normal. I closed Firefox, then relaunched. Same message. Did a logoff on my computer - same thing Did a full shutdown, login - same message. I got a bit radical - I dumped Firefox, deleted Trash. New installation (version 99.0.1) Same message;Close "Firefox. A copy of Firefox is already open. Only one copy of Firefox can be open at a time."

Currently using (newly installed) Edge for Mac, until this problem can be sorted; I hope it is brief, I have used Firefox for most of the years I have had a computer.

I have an iMac that is a decade old. Running macOS High Sierra version 10.13.6 That is as updated as I can get on this processor. I had a normal "there is a newer version of Firefox available" update alert, so relaunched Firefox to update. So on Monday 4th April NZ time i got the update. As usual I got the message [in a dialogue box]: '''Close Firefox. A copy of Firefox is already open. Only one copy of Firefox can be open at a time.''' So far, normal. I closed Firefox, then relaunched. Same message. Did a logoff on my computer - same thing Did a full shutdown, login - same message. I got a bit radical - I dumped Firefox, deleted Trash. New installation (version 99.0.1) Same message;Close "'''Firefox. A copy of Firefox is already open. Only one copy of Firefox can be open at a time.'''" Currently using (newly installed) Edge for Mac, until this problem can be sorted; I hope it is brief, I have used Firefox for most of the years I have had a computer.
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The funny thing that has happened is that, in answering the posting, Firefox opened the reply window; not Edge, where I had originally posted the query/problem. I am about to shut down and then relaunch Firefox; the problem may be no more? [fingers crossed] - let me see....

... and it has worked. Whatever has gone on in the background has resolved itself. I just don't have all the bookmarks I had anymore, and will need to reload all these, and the passwords [where needed], it will just take time.

Glad to back with Firefox.


p.s. I would like to cahnge Zioan's post to a favourable thumbs up, but I cannot edit this - sorry Zian.

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You can try uninstalling and reinstalling Firefox. Note that your old data will likely not be kept.

  1. In Applications in your Finder, locate the Firefox apps.
  2. If there are many of them, this could be the problem. Otherwise proceed to step 3. Move one of them at a time to Trash until the problem is fixed (you can always restore Trash items).
  3. Move Firefox to Trash and download a new release. Install it.

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I recently got that message and was able to restart Firefox after deleting the lock file. On my Linux system that is in the profile folder.

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I have iMac running system 10.13.6 As stated at the beginning, I had deleted Firefox, and then downloaded a fresh new install, which gave me the same problem.

I cannot find anything in the Appllication's Contents remotely like a lock-file; But thanks for the information.

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Chosen Solution

The funny thing that has happened is that, in answering the posting, Firefox opened the reply window; not Edge, where I had originally posted the query/problem. I am about to shut down and then relaunch Firefox; the problem may be no more? [fingers crossed] - let me see....

... and it has worked. Whatever has gone on in the background has resolved itself. I just don't have all the bookmarks I had anymore, and will need to reload all these, and the passwords [where needed], it will just take time.

Glad to back with Firefox.


p.s. I would like to cahnge Zioan's post to a favourable thumbs up, but I cannot edit this - sorry Zian.

Modified by gordon.bowers

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