Windows 10 Explorer Integration

After a new installation to version Nextcloud-2.6.2-setup, the Explorer integration is no longer available.A complete deinstallation and subsequent reinstallation is not successful. The checkbox for the integration was also unsuccessful. What can I do? The error occurs on two different PCs.
Regards Martin

Is it so difficult to use the search function of this forum?

Ok, many Thanks. I have not see it!