Yes it is..... I had also this same problem and I'm struggeling wiht it... For now I decided to stay on 5.4 (but the updates are not so often as for 5.6 and 6.0).... Fortinet selling extra FortiGuard Industrial Service now.... What i know that is yearly fee - so probably after everything will be not cheap. I tried get some infor from sales representative, but they want sell me the package what I have now and extra Industrial Service. I thin they want just a money for that and no other added value ;)
My answer is relatevly late - did you resolved somehow your problem?
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