Unfortunately I update Big Sur because of enhanced security promo and have no access to my ever 30,000 i-photos Help advice please HS

It might be that Big Sur doesn't know where your photos library is:

hold down the option key while starting photos, and see if your old library is listed then. If it is, open it.

Were you using iCloud to sync your photos (If you were, and all your photos are in iCloud then an alternative to the suggestions below is simply to let Icloud sync to the new Big Sur Library - it will take some time, possibly days and you need to keep photos open while it does it)

If not:

1 - In photos preferences (general), check which library is currently being opened by Big Sur, and where it is - post a screenshot of that if possible.

2 - Open finder, and look in your pictures folder. What libraries are in there? (Normally somthing.photoslibrary)

If there is more than one, then the old one will (probably) be the one that is named differently from the one in preferences. If there is more than one of those, you probably need the largest. Open it from the "other library" button above.

3 - If there is only the Big Sur library in pictures, then you are going to need to do a search in spotlight.

In finder, in the search bar, type "photoslibrary". Make sure it is searching "This Mac"

What does it find?

Hi - to help with diagnosis - can you answer the following?

• 
What version of MacOS did you upgrade from?
• Where is the library stored (System drive or external drive)? If external - what is the format of the drive?
• Is the library on a network drive or in some sort of cloud storage (EG Dropbox or NAS)?
• Do you use Icloud to sync photos?
• If so, do you have optimise local storage set?
• Did you take a backup of your system (or at least your photos library) before upgrade?
• What happens when you open photos, what do you see?