It was expected that signals weren't always perfect across great distances of space. They were especially unstable considering how fast the ships were moving that were sending and receiving signals.
On Basileus's trip over, he went through a few days unable to contact Varya and on the trip back it was the same.
However, the silver-haired empress couldn't help worrying herself sick over not receiving a communication from the prince for a few days. She went through each day with a lingering feeling in the back of her mind that something wasn't right.
Her biggest fear was finding that he had been shot out of the sky again. She thought of her son never being able to know his father memorably and the reality from before the prince came back alive was starting to set in again.