Could you please provide some more details such as software version running in the device.
Is there any specific changes done before you started seeing the issue ?
Is there any sudden power loss occurred in the device or any upgrades ?
Usually this error can occur when there is a mysql database update issue with the tables and also when there is some communication channels involved in the device.
Make sure that you receive the connection events for the same that you expecting dadhboard view.For that check if you enabled logging at end or beginning in access control rules. You can try a graceful reboot of the device also.
Verify the following from the device CLI.
pmtool status |grep SFData
pmtool status |grep sftunnel
pmtool status |grep mysqld
tail -90f messages
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As Ankita said, please check if logging is enabled. If logging is enabled then chances are SFTop10Cacher service is stuck or something. Please restart this service once and see if that fixes the issue:
-> Login to DC CLI
-> Become root
-> pmtool restartbyid SFTop10Cacher
This is what is called a hanging process or daemon. Technically it is bug. There shouldn't be a need to run the diagnostic tools, but it helps. It is not the first time this type of error occurs.