Hi, I encounter a similar problem. I have many plants connected with various version of the OZW. But in one in particular which has a 772.250 I can't connect. 

It tells me “Unknown Unicom Error (30)”. The strange thing is that since few days ago I could connect without problem with the plant.

Are you aware of some official help we can get from Siemens when we encouter these kind of problems?

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Split from Connection problem with OZW772.250 on the Remote Tool Access.

In these cases you need to restart the ozw, you should be able to do this by going to Faults > Services > Reboot web server