Well it's unlikely to be the temp sender and ignition unit both failing at once.

It's also unlikely to be the earth since they use the bike common earth, and the whole thing would have died if that failed.

However, I suspect the positive (power) to the instruments is from the same source, so I'd start by checking the fuses. If they're all fine, then check the plugs to the instruments are fully home - and check the pins are clean and not coroded.
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