There's 2 scenarios where an Error 603 is usually found..
1: VM require all your HDMI & TV kit to be HDCP2.2 compliant from V6 to TV, in order to watch certain content in 2160p - UHD. If any of your HDMI lead, any converters, splitters etc, or TV port are not HDCP2.2 compliant, Error 603 is the result.
To test this, follow Home > Help & Settings > Settings > Video Output > Video Format, and ensure 1080 is selected. If the error disappears, then HDCP2.2 is the problem.
2: When this requirement was first introduced, Samsung TV's seemed particularly prone to getting the same error when the HDCP2.2 compliance was in-place, and the error was more random in nature. A reboot might solve it etc, but it had all the feel of a bug rather than a replicable fault.
It's gone very quiet on scenario 2 since a little while, which suggests SW updates might have seen to it.
Check your video output in any case. You shouldn't need to necessarily reboot after applying any changes, but that's not a guarantee.
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