Currently it tell me that "this person ID cannot be found"
This is the second time in the past week I haven't been able to access the fan chart.
I just checked again and now the pedigree doesn't work eith.
Perhaps a screenshot of what you see might help get a better answer? If you are not selecting a Person and get that message - apparently it is opening with information on the person you 'last accessed' but no longer finds that person ID? I don't know what ID you would be getting that message about - except if it were the one 'starting the tree' (has current focus).
Check: https://www.familysearch.org/identity/settings/account Family Tree Starting Person to see if that is the person id the error message is referring to.
I cannot duplicate this issue on Operating System: Windows 11 21H2, Browser: Chrome Version 98.0.4758.82 (Official Build) (64-bit). I can view both the Pedigree and Fan Chart Tree views without error.
What Operating System and browser are you using?
What location are you connecting from (in Utah here - so close to FamilySearch HQ)?
Can a neighbor from your location bring up the Tree on their computer/smartphone without error?
Have you tried closing and reopening the browser?
Have you tried computer shutdown/restart?
You may want to consider contacting FamilySearch Support directly - via phone/chat (if available from your location):