"actuothenli" wrote: Same thing happened to me in Firefox 56.0 on Windows 10. The following from the support site topic "Some or all of my sites are gone! How do I get them back?" fixed the problem: "go to your LastPass icon -> More Options -> Advanced -> Clear local cache and then LastPass Icon -> More Options -> Advanced -> Refresh sites."
This works, but I've had to do this yesterday and today, there must be an issue somewhere. I too am using Firefox 56.0 (64-bit) on Windows 10