Under Stores -> Settings -> Configuration -> Sales -> Sales -> Minimum order amount I set Enable to Yes and Minimum Amount to 3000.
When I click Save Config the page refreshes, the message You saved the configuration. appears and the message One or more of the Cache Types are invalidated: Configuration, Page Cache. Please go to Cache Management and refresh cache types. appears, but the Enable and Minimum Amount values are back to the previous values.
So I go to the cache management, I refresh the invalidated caches, go back to the Configuration page and the options I saved are still back to the old values.
EDIT: I noticed it doesn’t work with other settings too. For example with Stores -> Settings -> Configuration -> Catalog -> Catalog -> Storefront -> Product Listing Sort By