Would you care to expand on that Please. What Application, what do you mean bounces.?

or try this : Please : https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer and https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles then https://support.mozilla.org/en-US/kb/refresh-firefox-reset-add-ons-and-settings TEST....... If no issues then Extensions which need to be added back in 1 at a time and tested ..... Or it is your Profile : Make a new one and test ...: https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles

Please let us know if this solved your issue or if need further assistance.

The application is Firefox for Mac, Version 57.0.1

BOUNCE EXPLAINED - On a Mac, there is a "ribbon" that contains all the "shortcuts" for all the applications you use frequently. In this case, the FireFox application is in that "ribbon".

Normally, when you want to launch (start) an application, you simply "single click" the short cut "Icon"in that ribbon. Once you single click... the Mac launches the application (Firefox) and you can "validate" the launch by virtue of the fact the application icon is "bouncing". Normally, the icon will continue to bounce until the application is running and the application window opens.

In this case, the application icon bounces "twice" then stops.

Normall, once the application has started and the application window is open, a "Black Dot" is added to the icon to let you quickly know which applications are open and which are not. Once the bouncing stops, there is no tale tale dot... regardless of how many times you try to launch, it will not.

However, if you simply "change the name" of the application (Firefox to Firefox1), the Firefox application will then open for a single session.

Thanks

Sounds like need to do a refresh or a uninstall and pull out all your folders except your profile https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profile your Profile may be the issue and then reinstall with Current Release Firefox 57.0.1 with a Full Version Installer https://www.mozilla.org/firefox/all/

https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles

https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile

Please let us know if this solved your issue or if need further assistance.

On Windows, there has in the past been malware that blocked browsers other than Internet Explorer from running. A workaround was to change the file name of firefox.exe to firefox1.exe. I would be surprised if this is an issue on your system, but you might want to do a scan just in case.

https://www.malwarebytes.com/antimalware/mac/

jscher2000 said

On Windows, there has in the past been malware that blocked browsers other than Internet Explorer from running. A workaround was to change the file name of firefox.exe to firefox1.exe. I would be surprised if this is an issue on your system, but you might want to do a scan just in case. https://www.malwarebytes.com/antimalware/mac/

Tried it but to no avail. Scan indicated I am clean. Good idea however...