I'm using Magento 2.3.
How can I fix Admin>Sales>Orders?
The list is not showing. I have orders but it's not showing.
You can check with below option, may be it will help to you.
Disable Asynchronous indexing from
Store > Configuration > Advance > Developer > Grid Settings
Note: The Developer tab and options are only available in Developer mode.
Updates : Asynchronous order data processing.
There can be times when intensive sales on a storefront occur at the same time that Magento is performing intensive order processing. You can configure Magento to distinguish these two traffic patterns on the database level to avoid conflicts between read and write operations in the corresponding tables. You can store and index order data asynchronously. Orders are placed in temporary storage and moved in bulk to the Order Management grid without any collisions. You can activate this option from Stores > Configuration > Advanced > Developer > Grid Settings > Asynchronous indexing.
You can get more information : DevDocs