Newsuser "Ian Stirling" wrote: ...

The lander was not coming on due to a timer, but running directly
from the solar panels as soon as the power produced by them got great
enough.

But communication sessions runs usually according to RTC timer.
In order to power up the transmitter, the lander had to initiate additional
power systems, which might drain almost empty batteries. If such a scenario
happened during a night, a failure is the most probably implication.

(STS)