Photo Library stored on external hard drive not opening.

I have my photo library stored on an external hard drive due to lack of space on my iMac, 21", M1 chip 2021. I had been able to open it even though it is formatted ExFat prior to upgrading to Sonoma. Now I get error message "The operation couldn’t be completed. (PHPhotosErrorDomain error 5416.)" How do I access my library?