All my pinned and most used shortcuts disappeared from firefox homepage?

This just happened to me 30 min ago. I think I found the fix. Here is what I did. Open a new tab like you have above. Then you go on the top right three bars, press help, then enter troubleshoot mode. It'll warn you that all your themes and extensions will be disabled. After that, everything popped up when it relaunched Firefox. For good measure, while it was in troubleshoot mode I made sure to sync and rename my profile.

Let me know if that works for you too. If you open a new window after closing one, it goes away, so this fix is only temporary I guess, which sucks.