Why is "Close existing connections" not active?

Question

Database administration

On some databases, through SQL Server Management, when trying to restore, the checkbox is not active:


And on other similar databases, it is active. Google says that it is necessary to install it, but not to say what to do when it cannot be installed, maybe some individual database setting.
As a workaround when restoring, I took the database offline (it was allowed to do this), then only performed a restore from the backup.

Answer 1

Network enrichment showed tips from disabling some automatic operations to restarting the server.
But most of all: enable this action before selecting a source, after which it will become unavailable, but remain enabled.
Other options .

Answer 2

It is customary to make inactive functions or options that do not make sense in a particular situation.
For example, there can be no connections to a database if the database is offline . Since there can be no connections, then there is nothing to close. Since there is nothing to close, the checkbox is made inactive.