I have upgraded to Magento 2.2.3 and most functions seem to work fine. However, when I try to add or modify a product in the catalog view, I always get an error 500.
How can I fix this?
Edit: when I go to web installation assistant, it gives an error 404.
If you are getting an error 500 you will find information into the webserver error log. Also, take a look to the Magento's logs too.
But I guess the webserevre error log will help you to find the reason of the error.