If you look at your database at the products table via phpMyAdmin ...

Do all of your products have set both the:
products_type
master_categories_id

If not, do you use Linked Products?

If not, you can fix the master_categories_id with the Tools ... Store Manager ...
Reset ALL Products Master Categories ID
to be used for Linked Products and Pricing:
click Reset ...

Then, fix the products_price_sorter from the Tools ... Store Manager ...
Update ALL Products Price Sorter
to be able to sort by displayed prices:
click Update ...

The Products Price Sorter cannot be fixed until *after* the master_categories_id is set ...

WARNING: before attempting anything ... backup your database

NOTE: if you do not have products_type set on your products, this should be fixed before doing anything ...