6.1.4 - Jobs not being processed (no unenryption configured)

Hello Experts,

I'm looking at an issue in a v6 environment where the jobs are not being processed (They get generated but just sit there in the jobqueue)

In the log, I see the messages repeatedly:

2017-12-21 10:37:39 +01:00 - Warning: Stopped task requests.

2017-12-21 10:37:39 +01:00 - Exception occured in ExecutionSlot (thread: Main Loop):

[821053] Could not decode parameter 'ConnectionString'.

    [809016] The encrypted value cannot be unencrypted. There is no unencryption configured.

           at VI.JobService.ExecutionSlot.Execute(Job job)

           at VI.JobService.ExecutionSlot._DecryptParameters(JobParameters parms)

           ---- Start of Inner Exception ----

           at VI.JobService.ExecutionSlot._DecryptParameters(JobParameters parms)

           at VI.Base.Encryption.NoEncryption.DecryptPartial(String data)

2017-12-21 10:37:39 +01:00 - VI.JobService.JobComponents.ScriptComponent - 6da4277d-7317-4b14-b46a-dd6e6cec8cc6: Errors occured

    [821053] Could not decode parameter 'ConnectionString'.

    [809016] The encrypted value cannot be unencrypted. There is no unencryption configured.

       at VI.JobService.ExecutionSlot.Execute(Job job)

       at VI.JobService.ExecutionSlot._DecryptParameters(JobParameters parms)

       ---- Start of Inner Exception ----

       at VI.JobService.ExecutionSlot._DecryptParameters(JobParameters parms)

       at VI.Base.Encryption.NoEncryption.DecryptPartial(String data)

I'm not sure if the above is causing all jobs not to be processed or just some jobs? Also, how can I debug this? In the service configuration I can see an encryption key file has been supplied...

Thanks

Kin