Please check in add-ons if they are still installed or there and greyed out. Please describe in detail what you find please.

Also, make sure the programs are up to date.

If you open a new Window when those toolbar buttons aren't showing, do those buttons then appear?

Also, if you place those toolbar buttons on the Navigation Toolbar (where the URL bar is placed) rather than on the Menu Bar (with File, Edit, View, History, etc) do the LastPass and "ad blockers" buttons still disappear on occasions?

I vaguely recall other users mentioning that LastPass was sensitive to having its toolbar button moved to anywhere except the Navigation Toolbar where the add-on placed it.

They suddenly disappeared yesterday from the menu bar yesterday.

I put them the navigation tool bar and they are still gone.

They have disappeared on every new page I open.

Thanks for your response - any ideas on how to restore are appreciated.

Some software, like Advanced SystemCare with Surfing Protection, can protect files in the Firefox profile folder against changes. If you have such software then check the settings or uninstall this software.

The file that saves the information about UI customizations is named xulstore.json and it might be corrupted.

• Use Help > Troubleshooting Information -> Profile Folder --> Show Folder to open your Profile folder
• Then close Firefox.
• Delete the xulstore.json fiile.
• Start Firefox and then do your Toolbar Customizations and see if it works now.

Thanks all for your support and help.

Issue seems to be resolved. Let's hope that it stays fixed.