Kerio Control hangs randomly anytime, thus stopping the users' access to the internet. The Gateway can't be pinged when Kerio Control is in this hung state. A reboot of Kerio Control resolves the issue temporarily.
Messages seen in the Warning logs when this happens:
[11/Dec/2020 16:37:43] Connection limit for source address 'vvv.xxx.yyy.zzz' reached (limit: 600)
[11/Dec/2020 16:38:16] Connection limit per minute for source address 'vvv.xxx.yyy.zzz' reached (limit: 1200)
The connection limits in Kerio Control should be increased or disabled (all set to zero) as per the steps in the Configuring connection limits in Kerio Control article.